
// Make newform 4050.2.c.x in Magma, downloaded from the LMFDB on 10 February 2025.
// To make the character of type GrpDrchElt, type "MakeCharacter_4050_c();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_4050_c_Hecke();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_4050_2_c_x();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_4050_2_c_x();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function ConvertToHeckeField(input: pass_field := false, Kf := [])
    if not pass_field then
        poly := [1, 0, -1, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 0, 0, 1], [-1, 0, 2, 0], [0, 2, 0, -1]];
    Rf_basisdens := [1, 1, 1, 1];
    Rf_basisnums := ChangeUniverse([[z : z in elt] : elt in Rf_num], Kf);
    Rfbasis := [Rf_basisnums[i]/Rf_basisdens[i] : i in [1..Degree(Kf)]];
    inp_vec := Vector(Rfbasis)*ChangeRing(Transpose(Matrix([[elt : elt in row] : row in input])),Kf);
    return Eltseq(inp_vec);
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_4050_c();"
function MakeCharacter_4050_c()
    N := 4050;
    order := 2;
    char_gens := [2351, 3727];
    v := [2, 1];
    // chi(gens[i]) = zeta^v[i]
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    F := CyclotomicField(order);
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),[F|F.1^e:e in v]);
    return MinimalBaseRingCharacter(chi);
end function;

// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_4050_c_Hecke();"
function MakeCharacter_4050_c_Hecke(Kf)
    N := 4050;
    order := 2;
    char_gens := [2351, 3727];
    char_values := [[1, 0, 0, 0], [-1, 0, 0, 0]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := true, Kf := Kf); // the value of chi on the gens as elements in the Hecke field
    F := Universe(values);// the Hecke field
    chi := DirichletCharacterFromValuesOnUnitGenerators(DirichletGroup(N,F),values);
    return chi;
end function;


function ExtendMultiplicatively(weight, aps, character)
    prec := NextPrime(NthPrime(#aps)) - 1; // we will able to figure out a_0 ... a_prec
    primes := PrimesUpTo(prec);
    prime_powers := primes;
    assert #primes eq #aps;
    log_prec := Floor(Log(prec)/Log(2)); // prec < 2^(log_prec+1)
    F := Universe(aps);
    FXY<X, Y> := PolynomialRing(F, 2);
    // 1/(1 - a_p T + p^(weight - 1) * char(p) T^2) = 1 + a_p T + a_{p^2} T^2 + ...
    R<T> := PowerSeriesRing(FXY : Precision := log_prec + 1);
    recursion := Coefficients(1/(1 - X*T + Y*T^2));
    coeffs := [F!0: i in [1..prec]];
    coeffs[1] := 1; //a_1
    for i := 1 to #primes do
        p := primes[i];
        coeffs[p] := aps[i];
        b := p^(weight - 1) * F!character(p);
        r := 2;
        p_power := p * p;
        //deals with powers of p
        while p_power le prec do
            Append(~prime_powers, p_power);
            coeffs[p_power] := Evaluate(recursion[r + 1], [aps[i], b]);
            p_power *:= p;
            r +:= 1;
        end while;    
    end for;
    Sort(~prime_powers);
    for pp in prime_powers do
        for k := 1 to Floor(prec/pp) do
            if GCD(k, pp) eq 1 then
                coeffs[pp*k] := coeffs[pp]*coeffs[k];
            end if;
        end for;
    end for;
    return coeffs;
end function;


function qexpCoeffs()
    // To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
    weight := 2;
    raw_aps := [[0, 1, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0], [0, 2, 1, 0], [0, 0, 0, -2], [0, -2, -1, 0], [0, 0, 2, 0], [1, 0, 0, 4], [0, 3, -2, 0], [0, 0, 0, 4], [2, 0, 0, 2], [0, 8, 0, 0], [0, 0, 0, 3], [0, -2, 2, 0], [0, -3, -2, 0], [0, 9, 2, 0], [0, 0, 0, -5], [2, 0, 0, -6], [0, 8, 0, 0], [-6, 0, 0, 0], [0, 4, -6, 0], [4, 0, 0, -6], [0, 12, -2, 0], [-12, 0, 0, 0], [0, 8, -4, 0], [-6, 0, 0, -2], [0, 10, 3, 0], [0, -12, 2, 0], [4, 0, 0, 8], [0, 6, 4, 0], [0, -10, -3, 0], [-12, 0, 0, -1], [0, 0, 6, 0], [13, 0, 0, 0], [-18, 0, 0, 0], [8, 0, 0, 6], [0, 2, 7, 0], [0, 4, -8, 0], [0, 0, -4, 0], [0, -3, -10, 0], [0, 0, 0, 7], [-16, 0, 0, 2], [-6, 0, 0, 2], [0, 16, 0, 0], [0, 15, -2, 0], [-2, 0, 0, 14], [5, 0, 0, -8], [0, 16, -2, 0], [0, -6, -6, 0], [-8, 0, 0, -8], [0, -12, 0, 0], [-12, 0, 0, 2], [-10, 0, 0, -4], [0, 0, 0, 7], [0, 18, 8, 0], [0, 9, -10, 0], [-6, 0, 0, -4], [14, 0, 0, 0], [0, 14, -1, 0], [12, 0, 0, -11], [0, -14, 10, 0], [0, -3, 6, 0], [0, 2, 6, 0], [-12, 0, 0, 2], [0, -14, 10, 0], [0, 21, -2, 0], [8, 0, 0, 0], [0, 14, -4, 0], [0, -6, 12, 0], [-2, 0, 0, 0], [0, 12, 6, 0], [-12, 0, 0, 2], [0, -4, 6, 0], [0, 4, 4, 0], [-23, 0, 0, -8], [0, -3, -2, 0], [6, 0, 0, 10], [0, -4, 8, 0], [24, 0, 0, 9], [7, 0, 0, 4], [0, 0, 0, -2], [20, 0, 0, -6], [18, 0, 0, 6], [0, 4, -4, 0], [-8, 0, 0, -6], [0, -18, -8, 0], [0, 0, 0, -19], [0, -10, -6, 0], [12, 0, 0, -12], [0, 10, -3, 0], [0, -6, 0, 0], [6, 0, 0, 4], [0, 2, -17, 0], [0, 0, 0, 7], [-17, 0, 0, 12], [0, -12, 4, 0], [-18, 0, 0, 0], [12, 0, 0, 3], [0, -2, 0, 0], [20, 0, 0, 4], [0, 2, 6, 0], [0, 9, -18, 0], [0, 0, 8, 0], [0, 0, 0, -7], [8, 0, 0, 4], [0, -4, -12, 0], [0, -12, -6, 0], [0, 0, 2, 0], [18, 0, 0, 0], [-1, 0, 0, 4], [0, -4, 18, 0], [0, -14, 15, 0], [0, 12, 6, 0], [-5, 0, 0, 12], [8, 0, 0, -16], [-24, 0, 0, 12], [0, 10, -6, 0], [0, -12, 20, 0], [0, 6, 4, 0], [24, 0, 0, -11], [-22, 0, 0, 6], [0, -8, -18, 0], [0, -9, 14, 0], [0, -6, 16, 0], [-19, 0, 0, -12], [24, 0, 0, 10], [4, 0, 0, 10], [-6, 0, 0, 24], [0, -34, 3, 0], [0, 16, 0, 0], [4, 0, 0, -24], [0, -24, 0, 0], [2, 0, 0, 12], [0, 14, -3, 0], [-12, 0, 0, -1], [34, 0, 0, -4], [0, 18, 4, 0], [0, -34, 0, 0], [0, 30, -8, 0], [36, 0, 0, 9], [-16, 0, 0, 8], [24, 0, 0, 10], [0, -8, -10, 0], [0, 18, 22, 0], [4, 0, 0, -24], [12, 0, 0, 0], [0, 28, -12, 0], [0, 18, 16, 0], [-32, 0, 0, -12], [0, -27, 10, 0], [0, 2, -17, 0], [-12, 0, 0, 24], [0, -20, -2, 0], [0, -15, -22, 0], [0, 14, -24, 0], [-36, 0, 0, -6], [4, 0, 0, -12], [24, 0, 0, 4], [0, 20, -8, 0], [12, 0, 0, -10], [0, 18, -2, 0], [0, 6, -14, 0], [0, -4, 6, 0], [0, 0, 0, -25], [0, -42, 0, 0], [0, -12, 28, 0], [32, 0, 0, -12], [0, 2, -3, 0], [7, 0, 0, 0], [0, -3, -14, 0], [12, 0, 0, -17], [8, 0, 0, -12], [36, 0, 0, -14], [0, -14, -22, 0], [22, 0, 0, -4], [-12, 0, 0, -11], [-31, 0, 0, -4], [6, 0, 0, -16], [0, 28, 14, 0], [4, 0, 0, -10], [0, 32, 14, 0], [48, 0, 0, -1], [0, 10, 3, 0], [0, 30, -10, 0], [0, 9, -26, 0], [24, 0, 0, 22], [0, 14, -9, 0], [0, -38, -8, 0], [1, 0, 0, 28], [18, 0, 0, 16], [0, -26, 16, 0], [0, -18, 4, 0], [8, 0, 0, 4], [0, 0, 0, 6], [0, -60, 0, 0], [0, 6, -10, 0], [-7, 0, 0, 0], [0, -26, 3, 0], [0, -12, -10, 0], [0, -21, 14, 0], [-12, 0, 0, -14], [-16, 0, 0, 0], [0, 2, -9, 0], [37, 0, 0, -12], [-36, 0, 0, 18], [0, -21, -10, 0], [-50, 0, 0, 4], [0, -36, -10, 0], [-24, 0, 0, 24], [8, 0, 0, -4], [0, 38, 8, 0], [6, 0, 0, -2], [0, 22, -21, 0], [0, -30, -18, 0], [6, 0, 0, -10], [35, 0, 0, 0], [0, 44, -2, 0], [24, 0, 0, 8], [0, 69, 2, 0], [0, 18, 12, 0], [-4, 0, 0, 2], [-2, 0, 0, -12], [12, 0, 0, 17], [0, -50, -3, 0], [0, -48, -12, 0], [-20, 0, 0, -28], [0, 18, 12, 0], [-24, 0, 0, 6], [0, -34, -1, 0], [-36, 0, 0, 5], [0, -26, 23, 0], [37, 0, 0, -12], [-4, 0, 0, 4], [48, 0, 0, -13], [0, -56, 12, 0], [0, 3, 2, 0], [-5, 0, 0, 0], [0, -18, 0, 0], [-12, 0, 0, 15], [54, 0, 0, 2], [0, 18, -22, 0], [-1, 0, 0, 36], [0, -26, -15, 0], [28, 0, 0, -6], [0, 18, -4, 0], [-12, 0, 0, -30], [0, -22, 5, 0], [12, 0, 0, -11], [37, 0, 0, 4], [0, 24, 20, 0], [0, -4, -36, 0], [-36, 0, 0, -5], [0, 48, -8, 0], [25, 0, 0, -12], [0, -27, 22, 0], [12, 0, 0, 25], [-4, 0, 0, 6], [0, -40, 0, 0], [0, -57, -10, 0], [0, -4, 24, 0], [0, 22, 19, 0], [0, 30, -12, 0], [-44, 0, 0, -12], [0, -2, -19, 0], [0, -24, 8, 0], [-23, 0, 0, 0], [-30, 0, 0, 4], [24, 0, 0, 21], [0, 16, 24, 0], [0, 45, 18, 0], [-10, 0, 0, 4], [0, -4, 12, 0], [0, -20, -30, 0], [-14, 0, 0, -6], [0, -58, 8, 0], [0, 16, -30, 0], [0, -6, 14, 0], [46, 0, 0, -8], [-31, 0, 0, 8], [-12, 0, 0, 31], [0, 27, -14, 0], [38, 0, 0, -6], [0, -9, -14, 0], [-22, 0, 0, -6], [0, -34, -6, 0], [24, 0, 0, 8], [0, 16, 14, 0], [0, 3, -2, 0], [34, 0, 0, -6], [0, 0, 0, -28], [6, 0, 0, 0], [0, 54, -10, 0], [0, -30, -4, 0], [-24, 0, 0, 2], [0, -2, -9, 0], [-6, 0, 0, 40], [-4, 0, 0, -10], [0, 42, 12, 0], [-12, 0, 0, 15], [0, -70, 0, 0], [0, -62, 6, 0], [0, 27, -14, 0], [-62, 0, 0, 14], [0, 36, 18, 0], [-7, 0, 0, 24], [0, -16, -2, 0], [0, -36, -6, 0], [-8, 0, 0, -18], [-42, 0, 0, -12], [0, 4, 0, 0], [0, -24, 20, 0], [-18, 0, 0, 8], [-36, 0, 0, -11], [0, -62, -2, 0], [0, -48, 0, 0], [37, 0, 0, 20], [-24, 0, 0, 11], [24, 0, 0, -20], [0, -8, 40, 0], [0, 0, 0, 20], [-25, 0, 0, 0], [0, 74, -2, 0], [24, 0, 0, 0], [0, 28, -2, 0], [0, -12, -6, 0], [17, 0, 0, -24], [-8, 0, 0, 12], [0, -50, 6, 0], [0, 27, -10, 0], [0, 21, -10, 0], [-28, 0, 0, -6], [0, -39, 6, 0], [-8, 0, 0, -26], [0, 18, 24, 0], [17, 0, 0, 24], [0, -18, 30, 0], [10, 0, 0, 12], [0, 24, -24, 0], [-19, 0, 0, -32], [0, -34, -15, 0], [0, -38, 31, 0], [0, 0, -36, 0], [42, 0, 0, -6], [26, 0, 0, 16], [0, 33, 26, 0], [-24, 0, 0, -2], [-4, 0, 0, -6], [0, -22, -8, 0], [12, 0, 0, -26], [0, 33, -10, 0], [-1, 0, 0, 16], [0, 44, -6, 0], [-18, 0, 0, 10], [0, 34, 3, 0], [58, 0, 0, -18], [0, 6, -32, 0], [36, 0, 0, -4], [-60, 0, 0, -7], [0, 18, 4, 0], [0, 69, -6, 0], [0, -52, 20, 0], [-24, 0, 0, -3], [0, -57, -18, 0], [24, 0, 0, 23], [0, 32, -6, 0], [0, 46, 2, 0], [0, 15, -30, 0], [0, 64, 18, 0], [-31, 0, 0, 4], [0, 0, 0, -19], [19, 0, 0, 8], [0, 3, -22, 0], [42, 0, 0, -2], [-4, 0, 0, -6], [0, 26, 29, 0], [-48, 0, 0, -1], [30, 0, 0, 40], [0, 10, -10, 0], [12, 0, 0, 40], [0, -10, -42, 0], [12, 0, 0, 46], [0, 42, 2, 0], [0, 50, 9, 0], [0, -30, -4, 0], [-32, 0, 0, -24], [0, -69, -2, 0], [-4, 0, 0, 12], [0, -10, -3, 0], [0, -62, 12, 0], [0, -15, 6, 0], [10, 0, 0, -20], [0, -45, 22, 0], [36, 0, 0, 10], [0, 14, -40, 0], [24, 0, 0, 30], [0, 40, -30, 0], [22, 0, 0, 16], [12, 0, 0, 15], [-25, 0, 0, 16], [6, 0, 0, 38], [16, 0, 0, 12], [0, 36, 26, 0], [0, 38, -19, 0], [0, 6, -22, 0], [48, 0, 0, -26], [38, 0, 0, 0], [0, 38, 5, 0], [-12, 0, 0, -31], [0, -20, 30, 0], [-24, 0, 0, -30], [0, 76, 10, 0], [0, 18, 40, 0], [0, 0, 8, 0], [-31, 0, 0, -12], [0, -28, -32, 0], [84, 0, 0, -8], [-6, 0, 0, 26], [0, -16, 50, 0], [0, -18, -4, 0], [0, 60, -4, 0], [-36, 0, 0, -32], [0, 38, -5, 0], [0, -27, 30, 0], [36, 0, 0, 1], [0, -14, 6, 0], [0, 39, -6, 0], [0, -36, -12, 0], [-24, 0, 0, 11], [-4, 0, 0, 0], [-24, 0, 0, 4]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_4050_c_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_4050_2_c_x();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose lines below.
// The precision argument determines an initial guess on how many Fourier coefficients to use.
// This guess is increased enough to uniquely determine the newform.
function MakeNewformModFrm_4050_2_c_x(:prec:=4)
    chi := MakeCharacter_4050_c();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(2999) - 1;
    while true do
        trunc_vec := Vector(Kf, [0] cat [f_vec[i]: i in [1..prec]]);
        B := Basis(S, prec + 1);
        S_basismat := Matrix([AbsEltseq(g): g in B]);
        if Rank(S_basismat) eq Min(NumberOfRows(S_basismat), NumberOfColumns(S_basismat)) then
            S_basismat := ChangeRing(S_basismat,Kf);
            f_lincom := Solution(S_basismat,trunc_vec);
            f := &+[f_lincom[i]*Basis(S)[i] : i in [1..#Basis(S)]];
            return f;
        end if;
        error if prec eq maxprec, "Unable to distinguish newform within newspace";
        prec := Min(Ceiling(1.25 * prec), maxprec);
    end while;
end function;


// To make the Hecke irreducible modular symbols subspace (type ModSym)
// containing the newform, type "MakeNewformModSym_4050_2_c_x();".
// This may take a long time!  To see verbose output, uncomment the SetVerbose line below.
// The default sign is -1.  You can change this with the optional parameter "sign".
function MakeNewformModSym_4050_2_c_x( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_4050_c();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<7,R![1, 0, 14, 0, 1]>,<11,R![-12, 0, 1]>,<13,R![1, 0, 14, 0, 1]>,<17,R![12, 0, 1]>,<19,R![-47, -2, 1]>,<29,R![-48, 0, 1]>,<41,R![-27, 0, 1]>,<71,R![6, 1]>],Snew);
    return Vf;
end function;