
// Make newform 462.2.j.d in Magma, downloaded from the LMFDB on 24 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_462_j();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_462_j_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_462_2_j_d();".
// 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_462_2_j_d();".
// 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, -1, 1, -1, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rfbasis := [Kf.1^i : i in [0..Degree(Kf)-1]];
    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_462_j();"
function MakeCharacter_462_j()
    N := 462;
    order := 5;
    char_gens := [155, 199, 211];
    v := [5, 5, 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_462_j_Hecke();"
function MakeCharacter_462_j_Hecke(Kf)
    N := 462;
    order := 5;
    char_gens := [155, 199, 211];
    char_values := [[1, 0, 0, 0], [1, 0, 0, 0], [0, 0, 0, -1]];
    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+1)]];
    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, -1, 1, -1], [0, 0, -1, 0], [-1, 0, -1, 0], [0, 0, 0, -1], [-1, 1, -3, -1], [-2, 2, -2, 2], [-1, -1, -1, 0], [0, 3, -3, 3], [0, 0, 3, -3], [4, -4, 0, -4], [-3, 4, -4, 3], [-3, 3, 0, 1], [0, -1, 2, -1], [10, 0, 0, 0], [0, -4, 4, -4], [6, -2, 2, -6], [2, -2, 0, 2], [10, -6, 10, 0], [4, 0, 10, -10], [4, -4, 4, 0], [10, -10, 0, -6], [-8, 12, -12, 8], [-2, -4, -2, 0], [2, 0, 11, -11], [-6, -4, 4, 6], [13, -12, 12, -13], [-9, 9, 0, 6], [0, 3, 3, 3], [9, 0, 3, -3], [0, -4, -14, -4], [8, 0, 8, 0], [0, 0, 0, 0], [2, -4, 2, 0], [1, -1, 0, 0], [0, 0, 0, 0], [0, -2, 6, -2], [0, -6, 0, -6], [-10, 10, -10, 10], [-16, 14, -14, 16], [0, -19, 7, -19], [0, 13, -8, 13], [6, -14, 6, 0], [1, -1, 0, 13], [-3, -20, -3, 0], [4, 0, -10, 10], [6, 0, 1, -1], [2, 12, -12, -2], [0, 9, 1, 9], [2, -2, 0, 4], [4, -4, 4, -4], [-4, 2, -2, 4], [0, 11, -19, 11], [0, 0, -18, 18], [-18, 22, -22, 18], [-5, 5, 0, 22], [-4, 0, -13, 13], [16, 2, 16, 0], [15, -15, 0, -15], [2, -11, 11, -2], [-18, 12, -18, 0], [0, -17, 2, -17], [-5, 5, 0, -11], [15, 0, 9, -9], [0, -4, 30, -4], [6, -14, 6, 0], [-6, -6, 6, 6], [6, 0, 2, -2], [7, -7, 0, -27], [-15, -12, -15, 0], [0, -2, 20, -2], [14, 0, 16, -16], [-27, 27, 0, 9], [-3, 3, 0, -13], [21, 0, 15, -15], [12, -2, 12, 0], [2, 14, -14, -2], [-12, 12, 0, 18], [-6, 0, 12, -12], [22, -2, 22, 0], [-14, 12, -12, 14], [24, 0, -8, 8], [0, 9, -3, 9], [27, -34, 34, -27], [-8, 8, 0, -10], [23, 0, -1, 1], [0, 3, 3, 3], [-30, 26, -26, 30], [20, -6, 20, 0], [34, 0, 8, -8], [10, 0, 30, -30], [16, -18, 16, 0], [-4, 16, -4, 0], [0, 20, 10, 20], [-15, 15, 0, 18], [4, -4, 0, -34], [0, -10, 14, -10], [0, 17, -4, 17], [-3, 3, 0, -15], [-5, -19, -5, 0], [-15, 10, -10, 15], [0, 6, 18, 6], [-16, 16, 0, 14], [42, -40, 40, -42], [0, 4, -30, 4], [-14, 0, 18, -18], [-28, 10, -28, 0], [4, -4, 0, -26], [19, 0, 17, -17], [5, -1, 5, 0], [24, -24, 0, -6], [10, 11, -11, -10], [0, -15, 9, -15], [-20, 0, -40, 40], [0, 3, 10, 3], [-30, 30, 0, 0], [0, 18, -24, 18], [-3, -37, -3, 0], [-16, -16, 16, 16], [-2, 2, 0, -18], [-15, 0, 5, -5], [-32, 0, -20, 20], [-22, 10, -10, 22], [16, -6, 16, 0], [-21, 0, -1, 1], [24, 1, -1, -24], [0, -16, 0, -16], [-15, 30, -15, 0], [36, -36, 0, -12], [-18, 0, -27, 27], [6, -6, 0, -42], [4, -22, 22, -4], [-3, -6, -3, 0], [0, 18, -28, 18], [-10, -9, 9, 10], [14, -34, 34, -14], [-24, 0, -14, 14], [0, -8, 18, -8], [21, -10, 21, 0], [-23, -8, -23, 0], [-20, 30, -20, 0], [0, 8, -8, 8], [4, -4, 0, 0], [12, 26, -26, -12], [18, -19, 19, -18], [-16, 16, 0, 22], [0, -22, 30, -22], [42, -18, 42, 0], [-30, 0, -36, 36], [-24, 0, 12, -12], [29, -26, 29, 0], [0, 4, 14, 4], [30, 0, -3, 3], [0, -24, 40, -24], [2, -2, 0, -2], [18, -20, 18, 0], [4, -32, 32, -4], [26, -42, 26, 0], [-3, 9, -3, 0], [18, -4, 4, -18], [5, 23, 5, 0], [-13, 0, -29, 29], [0, 0, 0, 12], [-30, 0, 0, 0], [0, 14, 26, 14], [12, -12, 12, -12], [-20, 20, 0, -18], [34, 0, 22, -22], [26, -26, 0, 16]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_462_j_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_462_2_j_d();".
// 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_462_2_j_d(:prec:=4)
    chi := MakeCharacter_462_j();
    f_vec := qexpCoeffs();
    Kf := Universe(f_vec);
    // SetVerbose("ModularForms", true);
    // SetVerbose("ModularSymbols", true);
    S := CuspidalSubspace(ModularForms(chi, 2));
    S := BaseChange(S, Kf);
    maxprec := NextPrime(997) - 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_462_2_j_d();".
// 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_462_2_j_d( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_462_j();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<5,R![1, 2, 4, 3, 1]>],Snew);
    return Vf;
end function;