
// Make newform 462.2.i.e in Magma, downloaded from the LMFDB on 18 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_462_i();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_462_i_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_i_e();".
// 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_i_e();".
// 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 := [49, 0, 7, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0], [0, 1, 0, 0], [0, 0, 1, 0], [0, 0, 0, 1]];
    Rf_basisdens := [1, 1, 7, 7];
    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_462_i();"
function MakeCharacter_462_i()
    N := 462;
    order := 3;
    char_gens := [155, 199, 211];
    v := [3, 2, 3];
    // 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_i_Hecke();"
function MakeCharacter_462_i_Hecke(Kf)
    N := 462;
    order := 3;
    char_gens := [155, 199, 211];
    char_values := [[1, 0, 0, 0], [0, 0, 1, 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+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 := [[0, 0, -1, 0], [1, 0, 1, 0], [0, 1, 0, 1], [0, 1, 0, 1], [-1, 0, -1, 0], [-4, 0, 0, 0], [3, 0, 3, 0], [0, 2, 0, 2], [0, -1, 0, -1], [2, 0, 0, 0], [4, 0, 4, 0], [0, 2, -4, 2], [9, 0, 0, 0], [4, 0, 0, -2], [0, -3, 4, -3], [-4, 0, -4, 0], [4, -4, 4, 0], [0, 3, 4, 3], [3, -4, 3, 0], [-8, 0, 0, -2], [10, 2, 10, 0], [0, 1, 8, 1], [5, 0, 0, -4], [0, -2, 8, -2], [-1, 0, 0, 4], [-2, -2, -2, 0], [0, 0, -10, 0], [0, 0, 9, 0], [-4, 3, -4, 0], [2, 0, 0, -4], [0, 0, 0, -1], [0, -4, -8, -4], [8, 2, 8, 0], [-2, 0, 0, 4], [0, 6, 4, 6], [-20, -1, -20, 0], [6, -2, 6, 0], [0, -4, 5, -4], [14, 0, 0, 2], [0, 0, 4, 0], [-10, 2, -10, 0], [0, 0, 0, 2], [0, -2, 12, -2], [0, 6, 0, 0], [6, 0, 0, -6], [-2, 8, -2, 0], [16, 0, 0, -2], [2, 0, 0, -10], [-13, 4, -13, 0], [0, -2, 12, -2], [0, 8, -1, 8], [8, 0, 0, 2], [6, 8, 6, 0], [18, 0, 0, -2], [0, 2, 4, 2], [-6, -6, -6, 0], [8, 1, 8, 0], [0, 2, 4, 2], [-4, 8, -4, 0], [-3, 0, 0, 0], [-4, -10, -4, 0], [-4, 0, 0, 4], [-22, 0, 0, -4], [-4, -7, -4, 0], [0, -4, -10, -4], [0, 5, -4, 5], [0, 0, 13, 0], [12, 0, 0, 2], [-19, -4, -19, 0], [0, 0, 0, 5], [18, 2, 18, 0], [0, 4, 10, 4], [-16, 2, -16, 0], [0, -9, 8, -9], [-17, 0, 0, 4], [0, -2, 24, -2], [-24, -3, -24, 0], [0, 0, 6, 0], [0, -6, -20, -6], [-20, -6, -20, 0], [6, 0, 0, 6], [22, 0, 0, 6], [12, 2, 12, 0], [-9, 0, 0, -4], [0, 1, -12, 1], [0, -8, -10, -8], [4, 0, 0, -10], [0, -4, -30, -4], [-14, 0, 0, 4], [2, 0, 0, -14], [0, 0, 8, 0], [18, 6, 18, 0], [-6, -6, -6, 0], [-1, 0, 0, 0], [0, -4, -8, -4], [4, 0, 0, 2], [0, 8, 4, 8], [-42, 0, -42, 0], [0, -2, 8, -2], [0, 9, -20, 9], [20, 0, 0, 2], [14, 2, 14, 0], [0, 0, 0, 0], [0, -8, 6, -8], [-2, 12, -2, 0], [9, -12, 9, 0], [-6, 0, 0, -6], [0, -12, 6, -12], [-32, 1, -32, 0], [-28, 0, 0, 4], [0, -11, 16, -11], [16, -9, 16, 0], [-20, 0, 0, -2], [41, 0, 41, 0], [26, 0, 0, -6], [16, 4, 16, 0], [20, 0, 0, 8], [-8, 13, -8, 0], [0, -11, -16, -11], [-3, 0, 0, 8], [-26, 2, -26, 0], [-30, 0, 0, -4], [0, 6, -24, 6], [-4, 8, -4, 0], [0, 8, -7, 8], [16, 0, 0, -10], [0, 12, -16, 12], [0, 3, -36, 3], [-2, 0, 0, 0], [0, 3, 4, 3], [14, 4, 14, 0], [-24, 0, 0, -2], [0, -2, -24, -2], [-22, 0, 0, 4], [0, 4, 37, 4], [-36, 0, 0, -2], [16, -3, 16, 0], [-4, -2, -4, 0], [16, 0, 0, -11], [-3, -16, -3, 0], [6, 0, 0, -4], [0, -16, 12, -16], [28, -6, 28, 0], [-7, 0, 0, -16], [-4, -6, -4, 0], [-8, 0, 0, 11], [-4, 0, 0, -7], [-31, 8, -31, 0], [0, 12, 17, 12], [0, -11, -4, -11], [0, -5, 24, -5], [2, 0, 0, -8], [-45, 0, 0, -4], [0, -14, 6, -14], [37, -8, 37, 0], [16, 0, 0, 13], [0, -1, 12, -1], [0, -10, -8, -10], [50, 0, 0, 0], [-14, 4, -14, 0], [0, 4, -26, 4], [-5, 0, 0, -12], [48, 0, 0, 3], [0, 0, 6, 0], [8, -8, 8, 0], [-24, -7, -24, 0], [28, 6, 28, 0], [-28, 8, -28, 0]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_462_i_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_462_2_i_e();".
// 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_i_e(:prec:=4)
    chi := MakeCharacter_462_i();
    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_i_e();".
// 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_i_e( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_462_i();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<5,R![49, 0, 7, 0, 1]>,<13,R![4, 1]>],Snew);
    return Vf;
end function;