
// Make newform 1950.2.f.o in Magma, downloaded from the LMFDB on 07 December 2025.
// To make the character of type GrpDrchElt, type "MakeCharacter_1950_f();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_1950_f_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_1950_2_f_o();".
// 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_1950_2_f_o();".
// 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 := [16, 0, 9, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 5, 0, 1], [5, 1, 1, 0], [-20, 9, -4, 1]];
    Rf_basisdens := [1, 4, 1, 4];
    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_1950_f();"
function MakeCharacter_1950_f()
    N := 1950;
    order := 2;
    char_gens := [1301, 1327, 301];
    v := [2, 1, 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_1950_f_Hecke();"
function MakeCharacter_1950_f_Hecke( : Kf := false)
    N := 1950;
    order := 2;
    char_gens := [1301, 1327, 301];
    char_values := [[1, 0, 0, 0], [-1, 0, 0, 0], [-1, 0, 0, 0]];
    assert UnitGenerators(DirichletGroup(N)) eq char_gens;
    values := ConvertToHeckeField(char_values : pass_field := ISA(Type(Kf), Fld), 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 := [[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 0, 0], [0, 1, 1, -1], [0, -1, 1, 1], [1, 2, 0, -1], [0, -2, 0, 0], [0, -6, 0, 0], [0, -1, 1, 1], [-2, 0, 0, 0], [0, 1, 1, 1], [2, -1, -1, 1], [0, -5, -1, -1], [0, -2, -2, -2], [0, -2, -2, 2], [0, -1, 3, 3], [0, 3, 1, 1], [10, 0, 0, 0], [-8, -1, -1, 1], [0, -2, 2, 2], [-10, 1, 1, -1], [-8, 0, 0, 0], [0, 2, 2, -2], [0, -1, -1, -1], [10, -1, -1, 1], [-6, 2, 2, -2], [0, -9, 1, 1], [0, 8, 0, 0], [0, 7, 1, 1], [0, 4, -2, -2], [0, 9, -1, -1], [4, 0, 0, 0], [-2, -4, -4, 4], [4, -4, -4, 4], [0, -14, 0, 0], [0, -1, 3, 3], [0, -9, 3, 3], [-4, 1, 1, -1], [16, -2, -2, 2], [0, 19, -1, -1], [-4, 4, 4, -4], [-14, 2, 2, -2], [4, -4, -4, 4], [-22, 1, 1, -1], [-10, 2, 2, -2], [-12, 2, 2, -2], [4, 0, 0, 0], [0, -3, -3, 3], [-8, 0, 0, 0], [0, -1, 1, 1], [0, -16, -2, -2], [0, -12, -4, -4], [0, 6, -2, -2], [20, -2, -2, 2], [0, 4, -2, -2], [0, -15, 3, 3], [10, -2, -2, 2], [0, -19, 1, 1], [0, 1, -7, -7], [0, -1, -1, -1], [0, -4, 0, 0], [10, -6, -6, 6], [-28, 1, 1, -1], [-4, -4, -4, 4], [0, 8, -2, -2], [-6, 0, 0, 0], [0, 16, 2, 2], [0, -6, 0, 0], [0, 6, -2, -2], [0, 7, -3, -3], [-6, 2, 2, -2], [0, 26, 2, 2], [0, -21, -3, -3], [0, 3, -1, -1], [0, -6, 0, 0], [8, 2, 2, -2], [-6, -2, -2, 2], [6, -3, -3, 3], [0, -11, -3, -3], [0, -8, -4, -4], [28, 0, 0, 0], [0, 13, 3, 3], [0, 16, -4, -4], [0, -18, 0, 0], [24, -4, -4, 4], [0, -20, -4, -4], [0, -33, -1, -1], [-22, 3, 3, -3], [0, -2, 4, 4], [0, 7, 7, -7], [0, 14, -2, -2], [0, 4, 4, 4], [-8, 3, 3, -3], [20, -6, -6, 6], [0, 18, -4, -4], [0, 23, -3, -3], [0, 24, -2, -2], [-6, -2, -2, 2], [0, -2, 6, 6], [0, -15, -1, -1], [0, 12, 8, 8], [-18, -2, -2, 2], [0, 0, 8, 8], [-6, -6, -6, 6], [4, 4, 4, -4], [-18, 3, 3, -3], [4, -4, -4, 4], [-18, -4, -4, 4], [24, -4, -4, 4], [38, 0, 0, 0], [0, -3, 3, 3], [30, -3, -3, 3], [22, -6, -6, 6], [0, 6, -8, -8], [0, 15, -5, -5], [-2, 0, 0, 0], [8, -3, -3, 3], [0, -9, 5, 5], [0, 15, 7, 7], [28, 2, 2, -2], [0, -5, 1, 1], [0, -6, -8, -8], [0, -17, -1, -1], [8, 8, 8, -8], [0, -4, 6, 6], [-14, 0, 0, 0], [0, 19, 5, 5], [20, 0, 0, 0], [0, 9, 7, 7], [26, -3, -3, 3], [0, 4, 10, 10], [-16, 0, 0, 0], [-20, 2, 2, -2], [0, -1, -1, -1], [0, -1, -1, -1], [0, 0, 8, 8], [-10, 2, 2, -2], [28, 5, 5, -5], [0, 3, 7, 7], [26, 4, 4, -4], [0, 36, 2, 2], [0, -36, 2, 2], [0, -47, -1, -1], [-20, -6, -6, 6], [18, -2, -2, 2], [0, -22, 6, 6], [14, -7, -7, 7], [0, 14, -4, -4], [12, 0, 0, 0], [0, 2, 2, -2], [22, 1, 1, -1], [22, -2, -2, 2], [0, -18, -2, -2], [0, 23, 1, 1], [0, -34, -2, -2], [4, 0, 0, 0], [28, 2, 2, -2], [0, -9, -9, -9], [0, 12, -2, -2], [0, 14, 0, 0], [4, 4, 4, -4], [0, -10, -8, -8], [32, -5, -5, 5], [44, 2, 2, -2], [-14, -6, -6, 6], [-48, 4, 4, -4], [-12, 6, 6, -6], [0, 7, 11, 11], [0, -14, 2, 2], [0, 23, 3, 3], [0, 5, 3, 3], [0, 3, 9, 9], [-4, 8, 8, -8], [-2, -3, -3, 3], [-16, 4, 4, -4], [-30, 10, 10, -10], [0, -8, 2, 2], [0, -10, -4, -4], [0, 15, 9, 9], [22, -4, -4, 4], [-32, 1, 1, -1], [4, 0, 0, 0], [0, -15, 1, 1], [30, 0, 0, 0], [-16, -6, -6, 6], [6, 4, 4, -4], [0, 7, 3, 3], [16, -5, -5, 5], [0, 8, -12, -12], [0, 2, 2, 2], [0, 0, 2, 2], [16, -10, -10, 10], [20, -8, -8, 8], [0, -46, 0, 0], [0, -2, -6, -6], [0, 16, -2, -2], [0, 22, -6, -6], [0, 15, 3, 3], [34, 4, 4, -4], [0, -27, 3, 3], [0, 18, -8, -8], [28, -2, -2, 2], [14, 3, 3, -3], [14, 0, 0, 0], [0, -53, 1, 1], [0, -9, -1, -1], [0, -33, -1, -1], [0, -32, 0, 0], [0, 29, -3, -3], [-12, 8, 8, -8], [0, -6, 8, 8], [-26, 0, 0, 0], [0, -5, 5, 5], [28, 6, 6, -6], [0, 10, 2, 2], [0, -12, 4, 4], [0, 17, -1, -1], [46, -6, -6, 6], [0, 0, 0, 0], [-62, 2, 2, -2], [10, -2, -2, 2], [0, 1, -7, -7], [0, -9, -13, -13], [0, 1, 1, -1], [0, -4, -8, -8], [26, -8, -8, 8], [0, -16, -2, -2], [12, -6, -6, 6], [0, 33, 7, 7], [0, -23, 3, 3], [0, 33, 5, 5], [4, 0, 0, 0], [0, 17, -11, -11], [2, 10, 10, -10], [0, 32, 4, 4], [-24, -4, -4, 4], [0, 56, 4, 4], [-10, 12, 12, -12], [-4, -8, -8, 8], [16, 2, 2, -2], [-20, 12, 12, -12], [-60, 0, 0, 0], [0, -11, -5, -5], [0, -9, -3, -3], [38, -6, -6, 6], [-52, 8, 8, -8], [8, 1, 1, -1], [0, 3, -7, -7], [0, 6, -4, -4], [0, 13, 11, 11], [22, -5, -5, 5], [0, -1, -5, -5], [8, -8, -8, 8], [14, 6, 6, -6], [0, -67, 1, 1], [0, 17, 7, 7], [26, -16, -16, 16], [36, 3, 3, -3], [0, 19, -1, -1], [-42, 3, 3, -3], [0, 9, -9, -9], [0, 36, 8, 8], [0, -7, 7, 7], [0, -29, 3, 3], [10, -8, -8, 8], [-28, -4, -4, 4], [0, -6, 4, 4], [0, -29, -9, -9], [-40, 1, 1, -1], [0, -27, 5, 5], [-2, 6, 6, -6], [16, -5, -5, 5], [-30, -9, -9, 9], [12, -2, -2, 2], [0, 10, -16, -16], [-56, -5, -5, 5], [-16, 0, 0, 0], [0, 13, 15, 15], [0, 30, 2, 2], [28, -10, -10, 10], [0, 67, -3, -3], [0, 43, -5, -5], [0, -37, -3, -3], [0, 13, -1, -1], [-36, 1, 1, -1], [16, 12, 12, -12], [0, 66, -4, -4], [58, -6, -6, 6], [0, 59, 3, 3], [14, 12, 12, -12], [14, -12, -12, 12], [0, -34, -10, -10], [22, 6, 6, -6], [0, -29, 9, 9], [0, -9, -17, -17], [50, -2, -2, 2], [-40, 8, 8, -8], [0, 15, -9, -9], [-36, -6, -6, 6], [-56, 7, 7, -7], [0, 40, 2, 2], [2, 14, 14, -14], [-12, 10, 10, -10]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_1950_f_Hecke( : Kf := Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_1950_2_f_o();".
// 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_1950_2_f_o(:prec:=4)
    chi := MakeCharacter_1950_f();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(1999) - 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_1950_2_f_o();".
// 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_1950_2_f_o( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_1950_f();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<7,R![-16, -2, 1]>,<11,R![256, 0, 36, 0, 1]>,<19,R![36, 0, 1]>,<37,R![-16, -2, 1]>],Snew);
    return Vf;
end function;