
// Make newform 668.2.a.c in Magma, downloaded from the LMFDB on 23 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_668_a();"
// To make the coeffs of the qexp of the newform in the Hecke field type "qexpCoeffs();"
// To make the newform (type ModFrm), type "MakeNewformModFrm_668_2_a_c();".
// 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_668_2_a_c();".
// 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 := [-4, -4, 17, 21, -7, -11, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0, 0, 0, 0], [0, 1, 0, 0, 0, 0, 0], [-50, 5, 149, 13, -73, -6, 7], [-58, 35, 191, -1, -95, -6, 9], [70, -31, -263, -11, 135, 10, -13], [33, -18, -123, 0, 63, 4, -6], [-154, 81, 565, 1, -285, -18, 27]];
    Rf_basisdens := [1, 1, 4, 4, 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_668_a();"
function MakeCharacter_668_a()
    N := 668;
    order := 1;
    char_gens := [335, 5];
    v := [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;

function MakeCharacter_668_a_Hecke(Kf)
    return MakeCharacter_668_a();
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, 0, 0, 0, 0, 0], [-1, 0, 0, -1, 0, 0, 0], [0, 1, -1, 1, 0, 0, 0], [-2, -1, 1, 0, 0, -1, 0], [-1, 0, 1, 0, 1, 1, 2], [0, 1, 1, 1, 1, 1, 0], [0, -2, 0, 0, -1, -1, -2], [-1, -1, -2, 1, 0, 0, -1], [-4, 0, 2, -2, -1, -1, 0], [0, 0, -2, 1, -1, 0, -2], [-4, 2, 0, -2, -3, 2, 3], [-2, 1, 1, 1, 4, 0, 0], [0, -3, 1, 1, 2, -2, 0], [-4, 1, -1, -1, 0, 0, 0], [-1, 2, 1, -2, 0, 2, -1], [-2, 0, -2, -2, -2, -2, 0], [-2, -2, 2, -2, 0, 0, 2], [-1, 2, -2, 1, 3, -1, 2], [-6, -1, -1, 1, 2, 0, 2], [4, -1, 1, 1, 3, 1, -2], [2, -2, 2, -4, -3, 1, 0], [0, 1, -3, 3, -2, -2, -4], [0, -1, -1, -1, -6, 2, 2], [3, -3, 5, 2, 5, -1, 2], [-1, -1, 4, 1, 0, -2, 0], [4, 3, 1, 1, 4, 0, 0], [0, 1, -1, 5, 3, -1, 0], [-2, 0, 0, -1, 3, -4, 2], [-2, 0, 4, -4, -2, 0, -2], [-2, 5, -1, -1, 0, -2, 2], [-3, 1, -4, 3, -3, 3, 2], [2, 3, 3, -3, 0, 2, 6], [7, 2, -3, 2, 3, 3, -2], [-4, 5, -3, -1, -3, -3, 2], [6, -2, -2, 2, -1, 5, -2], [-6, 2, 2, -4, -1, -3, 0], [-8, -1, 1, -3, 1, -2, 1], [-6, -2, 4, 2, 2, -4, -6], [1, 0, 0, 0, 0, 0, 0], [-3, 5, 6, -5, -1, 1, 2], [3, -5, 0, 5, 5, -3, -7], [3, -9, 2, -3, -2, 0, -3], [4, 7, -5, -3, -4, 1, -1], [-2, 3, 3, -5, 3, 7, 10], [-6, 2, -4, 2, -3, -1, 0], [-9, -5, 2, -3, -2, -4, 0], [-4, -10, -2, 2, -6, -1, -7], [-5, 2, -2, 1, 0, 0, 0], [2, 1, -3, -3, 2, 6, 2], [4, -6, 2, 9, 8, -1, 0], [0, 8, -4, -4, 0, 1, 5], [1, -1, 3, 6, -2, 0, -4], [-4, -1, -1, -3, -1, -3, 0], [10, -2, -2, 1, -9, 0, -2], [2, -7, 3, 1, -3, 1, -6], [1, 0, -2, 5, 5, -7, -6], [-12, 3, -3, -1, 1, 3, 8], [10, -4, 0, 6, 4, 4, 2], [-4, 0, 0, 4, 3, -3, -6], [5, 10, -10, 7, -5, 3, -6], [-3, 0, -5, 4, -1, 3, -2], [4, 2, 0, 6, 1, 0, -3], [-2, 2, 0, 0, 1, 1, 0], [4, -3, 1, -1, 2, -4, -4], [4, 7, -9, -1, 1, -1, -6], [-5, -5, 5, 4, 4, 2, 4], [4, -3, -5, 7, -2, -2, 2], [-3, -2, 3, -2, -2, 2, 3], [-10, -5, 5, -3, -1, 1, 2], [-2, 3, -5, 1, -8, 8, -6], [0, -3, 3, 2, 3, 4, -2], [4, -1, 5, -11, 1, 2, 5], [-11, 8, -3, 0, 0, 2, -3], [-4, -2, 4, -8, -3, 7, 8], [-8, 5, 7, -7, 2, 4, 8], [6, -6, -6, 5, -7, -2, -10], [2, -7, -1, 3, 0, 2, 0], [-11, -6, 8, -9, -4, -4, 0], [-2, 0, -4, 4, -7, 1, 0], [9, -8, 7, 0, 0, 0, -4], [-20, -3, 3, -5, 1, -4, 7], [-8, 1, -5, 4, -3, 0, -2], [3, -3, -1, 10, 3, -7, -10], [11, 1, -2, 11, -3, -5, -5], [6, -7, -5, 1, -4, -4, -4], [-4, -7, 5, -3, -5, -7, -2], [5, -2, -1, -2, -2, 6, 3], [6, -7, 3, -1, 3, 5, -4], [9, -1, -2, 5, 9, 3, -3], [-4, 7, 1, 7, 0, 0, -4], [2, 4, -2, 11, 0, -3, -4], [-4, 4, -2, 0, -2, 8, 4], [-18, 5, 1, -9, -10, 2, 4], [8, 9, -7, 7, 10, 0, 0], [-8, 4, 8, -6, 11, -1, 8], [11, 3, 15, -4, 8, 2, 8], [-13, 4, 1, -8, 0, 4, 8], [4, 0, -2, -2, -2, 2, 4], [16, 1, -5, 15, 5, 2, 1], [-12, 5, -3, -11, -4, 2, 8], [0, 6, -4, 6, -3, 5, 8], [3, -13, 10, -7, -1, 5, 2], [3, -7, 10, -5, -9, 3, 1], [0, 7, 1, -15, -4, 6, 10], [4, -2, -6, 2, -3, 1, -8], [-4, 7, -13, 1, -4, -3, -13], [18, 4, 6, 10, 11, -1, 2], [30, 1, -5, 13, 4, 2, -6], [6, -6, 12, -1, -4, -1, -4], [0, -1, 15, -6, 8, -5, 8], [16, -9, 7, 3, 3, 1, -8], [-8, 3, -5, -3, 4, -9, 5], [-16, -8, 6, -3, -9, 4, -2], [18, 0, -6, 8, 2, -2, -6], [-9, -9, 11, -12, -2, 0, 8], [12, -9, 1, -1, 1, -3, -6], [-4, -7, 13, 3, 13, -3, 6], [2, 12, 2, -6, 3, 3, 8], [-8, -1, -5, 5, 2, 3, -1], [-10, -8, -2, -8, -12, -2, 0], [0, -4, 8, -4, -3, -7, -4], [16, -2, -10, 12, -8, 2, -2], [-2, 2, -2, -2, -6, -6, -8], [-6, -1, -7, 5, 5, -3, -2], [-4, -7, -3, -3, -4, -4, -8], [-3, 4, 8, 1, 13, -7, 6], [-10, -13, 9, -3, -11, 3, 2], [-2, 3, -5, -3, -1, -9, -8], [-6, 4, 8, -2, 13, -9, 6], [-15, 1, 6, -9, 6, 8, 3], [0, -4, 6, -2, 1, 5, 6], [4, 8, -2, 4, -7, 1, 6], [-4, -11, 3, 1, 6, -2, -8], [-15, -8, -1, 0, -4, -4, -4], [-17, 7, -15, -8, -10, 4, 4], [-2, 11, -7, -13, -14, 4, 4], [0, 14, -12, 12, 10, -4, -4], [-2, -2, -6, -8, -14, -2, -2], [-8, -11, -9, 11, -8, -6, -14], [-9, -3, -2, -9, -16, 6, 0], [-2, 11, 1, -5, 0, 6, 0], [-6, -6, 10, -2, -1, -11, 6], [2, -1, -9, 1, -7, -1, -14], [20, -6, 8, 10, 9, 5, -2], [12, 6, 14, -12, 6, 12, 10], [-9, 12, -2, -5, -7, 9, 10], [-9, 6, 3, 2, 10, -6, 4], [-13, 0, -3, 8, 5, -11, -5], [6, -5, 7, 0, -7, -8, -6], [-9, 8, 7, 0, 6, -2, 4], [1, -5, -10, 1, 1, -5, 1], [12, -10, -2, 2, -2, -10, -2], [-10, 9, -17, 8, -6, 11, 0], [-6, 5, -13, -7, -12, 8, 6], [-5, -10, 12, -7, -5, -1, 2], [-15, 8, -3, -4, 0, 10, 17], [9, -8, 3, 12, 11, -3, -5], [-16, 3, -1, -11, 4, 1, 7], [14, -6, 8, 6, 12, 4, 4], [-6, 7, -9, -13, -2, 8, 18], [-1, 0, -20, 7, -2, 2, -8], [12, -4, -16, 6, -1, 3, 0], [-16, -17, 7, -11, -10, -5, -9], [6, -15, 7, -11, -12, -6, -12], [-6, 13, -5, -9, -15, 3, 4], [-2, 0, -6, 4, 8, -6, 2], [-10, 4, 4, -2, 10, 8, 8], [-16, 3, 1, -10, -9, -6, -10]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_668_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_668_2_a_c();".
// 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_668_2_a_c(:prec:=7)
    chi := MakeCharacter_668_a();
    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_668_2_a_c();".
// 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_668_2_a_c( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_668_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<3,R![-7, 4, 29, -6, -32, -6, 4, 1]>],Snew);
    return Vf;
end function;