
// Make newform 975.2.n.o in Magma, downloaded from the LMFDB on 01 May 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_975_n();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_975_n_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_975_2_n_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_975_2_n_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 := [1, 2, 2, -8, 14, -2, 0, 0, 1];
        Kf := NumberField(Polynomial([elt : elt in poly]));
        AssignNames(~Kf, ["nu"]);
    end if;
    Rf_num := [[1, 0, 0, 0, 0, 0, 0, 0], [0, 1, 0, 0, 0, 0, 0, 0], [574, -65, -69, 236, 48, 1, 4, 16], [-67, -402, 1448, -1009, 130, 16, 64, -63], [63, 59, -276, 944, -127, 4, 16, 64], [268, -1582, 1545, -1068, 118, -64, 63, -67], [134, 804, -2577, 2018, -260, -32, -128, 126], [-575, -579, 2276, -3522, 511, 4, 16, -255]];
    Rf_basisdens := [1, 1, 319, 319, 319, 319, 319, 319];
    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_975_n();"
function MakeCharacter_975_n()
    N := 975;
    order := 4;
    char_gens := [326, 352, 301];
    v := [2, 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_975_n_Hecke();"
function MakeCharacter_975_n_Hecke(Kf)
    N := 975;
    order := 4;
    char_gens := [326, 352, 301];
    char_values := [[-1, 0, 0, 0, 0, 0, 0, 0], [-1, 0, 0, 0, 0, 0, 0, 0], [0, 0, 0, -1, 0, 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 := [[1, 0, 0, -1, -1, 0, 0, 1], [0, 1, -1, 0, 0, 1, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0], [2, 0, 1, -2, 1, 0, 1, 1], [0, 0, 0, 0, -1, 0, 0, 2], [2, 0, 0, 0, -1, -1, 1, 0], [0, -1, 0, -3, 0, -1, 0, -1], [0, 0, 0, 0, 2, 0, 0, -1], [0, -1, 0, 5, 0, -1, -1, -1], [0, -2, 0, -1, 1, -3, -2, -3], [-2, 0, -2, 2, -1, 0, -2, -2], [0, 0, 0, 0, 2, 0, 0, -1], [-4, -1, 1, -4, 0, -3, -1, 0], [1, -2, 1, 0, -1, -3, 0, 3], [-3, 4, 0, -3, 0, 1, 0, 0], [4, -6, 5, 0, 5, -1, 0, 1], [-3, 0, -4, 3, -3, 0, -4, -5], [-1, -5, 0, 0, 5, 0, 0, 0], [2, -9, 3, 2, 0, -8, -3, 0], [1, 3, 1, 1, 0, 1, -1, 0], [0, 0, 5, 0, -2, 0, 5, 5], [5, 3, -3, 0, 1, 4, 0, -4], [-4, 0, 2, 4, 1, 0, 2, 3], [5, 0, 2, -5, -4, 0, 2, 6], [2, -8, 2, 2, 0, -6, -2, 0], [-4, 7, -1, 0, -2, 5, 0, -5], [-11, 0, 1, 0, -1, -1, 0, 1], [-2, 4, 2, 0, -3, 1, 0, -1], [1, 0, -3, -1, 0, 0, -3, 1], [-2, 2, 0, 0, -1, 1, 0, -1], [-5, 3, -1, 0, -4, -1, 0, 1], [0, -3, 0, -3, -4, 1, 1, 1], [-3, 0, -6, -3, 0, 4, 6, 0], [0, 2, 0, 0, -2, 0, 0, 0], [-2, -10, 6, -2, 0, -4, -6, 0], [-6, -8, 2, -6, 0, -3, -2, 0], [0, 5, 0, 4, 1, 4, 11, 4], [-4, 0, 2, 4, 8, 0, 2, -5], [-1, -9, 0, -1, 0, -1, 0, 0], [0, -8, 0, 4, -6, -2, -1, -2], [9, 7, -1, 0, -7, 0, 0, 0], [0, 0, 0, 2, 4, -4, -7, -4], [0, -3, 0, 2, 2, -5, -6, -5], [-1, 0, 5, 1, 8, 0, 5, 5], [12, 0, 3, -12, 6, 0, 3, 3], [0, 6, 0, 4, 4, 2, 4, 2], [11, 2, 5, 0, -4, -2, 0, 2], [5, 3, -7, 5, 0, -1, 7, 0], [-4, 0, -9, 4, -1, 0, -9, -8], [-3, -10, 10, -3, 0, -8, -10, 0], [0, -4, 0, -8, 3, -7, -4, -7], [0, 0, -4, 0, 0, 3, 4, 0], [-5, 1, -5, -5, 0, -3, 5, 0], [3, 6, -15, 0, -3, 3, 0, -3], [0, 2, 0, 8, -3, 5, 9, 5], [1, 2, 7, 0, -1, 1, 0, -1], [0, -2, 0, 5, 4, -6, -2, -6], [-6, 10, -2, -6, 0, 9, 2, 0], [-2, 9, -8, 0, -1, 8, 0, -8], [7, 0, 2, -7, 6, 0, 2, 0], [0, 9, -12, 0, -6, 3, 0, -3], [1, 8, -2, 1, 0, -4, 2, 0], [3, 0, 8, -3, 10, 0, 8, 3], [-12, 1, 0, 0, 2, 3, 0, -3], [0, -5, 0, -4, -5, 0, -15, 0], [5, 0, 8, -5, 2, 0, 8, 9], [0, 0, -2, 0, 8, 0, -2, -13], [-4, 7, -13, 0, -2, 5, 0, -5], [-16, 0, 2, 0, 6, 6, 0, -6], [-2, 1, 4, -2, 0, -5, -4, 0], [1, 0, -6, -1, -10, 0, -6, 5], [12, 0, 8, -12, 7, 0, 8, 9], [0, 3, 0, -16, -4, 7, 2, 7], [0, 6, 0, 2, 6, 0, 3, 0], [1, 0, 0, -1, 9, 0, 0, -2], [8, 0, -2, -8, -4, 0, -2, 9], [4, 2, -6, 0, 7, 9, 0, -9], [-2, 0, 0, 2, -8, 0, 0, -4], [1, 0, 9, -1, -8, 0, 9, 11], [-5, 0, -8, 5, 0, 0, -8, -11], [0, 6, 0, 1, 11, -5, -1, -5], [-5, 0, 3, 5, 4, 0, 3, 6], [-5, 23, -3, -5, 0, 19, 3, 0], [6, 12, -2, 0, -3, 9, 0, -9], [0, -15, 0, 15, -8, -7, -15, -7], [-9, 2, -5, 0, 13, 15, 0, -15], [-2, 0, 2, 2, 6, 0, 2, 16], [-9, -7, -4, -9, 0, 3, 4, 0], [15, -10, 2, 15, 0, -14, -2, 0], [-9, 0, -7, 9, -7, 0, -7, -4], [0, -4, 0, -20, -9, 5, -4, 5], [13, 0, -6, -13, -13, 0, -6, 4], [-5, -11, 2, -5, 0, -12, -2, 0], [-8, -1, 4, 0, -2, -3, 0, 3], [2, 0, -2, -2, 7, 0, -2, -5], [5, -11, 7, 0, -2, -13, 0, 13], [2, -11, 8, 2, 0, -1, -8, 0], [0, 2, 0, 0, 2, 0, 6, 0], [0, 4, 0, 6, 3, 1, 0, 1], [-6, -15, 7, -6, 0, -19, -7, 0], [0, 7, 0, 1, 11, -4, -5, -4], [3, 3, 1, 3, 0, -11, -1, 0], [0, -1, 0, 7, 0, -1, 5, -1], [28, -4, 1, 0, -6, -10, 0, 10], [0, 3, 0, -1, 0, 3, -7, 3], [5, 4, 3, 5, 0, -16, -3, 0], [4, 0, -7, -4, -13, 0, -7, -6], [10, 6, 3, 10, 0, 6, -3, 0], [0, -7, 0, -11, -14, 7, 1, 7], [-22, 16, -9, 0, 1, 17, 0, -17], [0, 8, 0, 10, 7, 1, -10, 1], [-7, -10, -2, -7, 0, -6, 2, 0], [8, 0, 10, -8, 6, 0, 10, 30], [-4, 7, 1, -4, 0, 13, -1, 0], [-9, -5, 2, -9, 0, 19, -2, 0], [17, 0, 6, 0, -12, -12, 0, 12], [10, 9, -10, 10, 0, 9, 10, 0], [0, 6, 0, -16, 13, -7, 2, -7], [-17, 2, -4, 0, 8, 10, 0, -10], [0, 6, 0, 13, 1, 5, 1, 5], [-2, 15, 1, -2, 0, 13, -1, 0], [16, -3, -5, 0, 8, 5, 0, -5], [-8, 0, -10, 0, 0, 0, 0, 0], [-2, 11, -9, -2, 0, 14, 9, 0], [4, 0, -9, -4, 9, 0, -9, -13], [-17, -5, 10, 0, 7, 2, 0, -2], [14, 13, -1, 14, 0, -1, 1, 0], [-11, 11, -9, 0, 3, 14, 0, -14], [19, 4, -5, 0, -11, -7, 0, 7], [-11, 26, -7, -11, 0, 24, 7, 0], [9, 3, -11, 9, 0, 2, 11, 0], [5, 0, -10, -5, 17, 0, -10, -20], [0, -1, 0, 1, -8, 7, -7, 7], [0, 1, 0, 1, -8, 9, 12, 9], [-21, 0, -4, 21, 2, 0, -4, 5], [0, 0, -3, 0, -20, 0, -3, 10], [0, 0, 2, 0, -16, 0, 2, 0], [8, 0, 8, -8, 13, 0, 8, 8], [0, -5, 0, 31, -9, 4, -2, 4], [0, 2, 0, 8, 7, -5, 16, -5], [-3, 0, -5, 3, -17, 0, -5, -15], [-11, -13, 7, -11, 0, -1, -7, 0], [28, -21, 14, 0, 5, -16, 0, 16], [10, -5, 3, 10, 0, -18, -3, 0], [0, 16, 0, -17, 13, 3, 12, 3], [9, 0, 1, -9, 10, 0, 1, 3], [4, 0, -2, -4, 6, 0, -2, -2], [0, 9, 0, -16, 8, 1, 14, 1], [-11, 4, 1, 0, -9, -5, 0, 5], [-19, 0, 1, 19, 17, 0, 1, -6], [6, -16, 11, 6, 0, -10, -11, 0], [2, -12, 1, 0, 17, 5, 0, -5], [12, 6, 8, 0, -3, 3, 0, -3], [-21, -13, -9, 0, 9, -4, 0, 4], [-4, -5, 12, 0, -2, -7, 0, 7], [0, 2, 0, 21, 10, -8, 17, -8], [-2, 11, -34, 0, -5, 6, 0, -6], [-7, -14, 18, -7, 0, -16, -18, 0], [0, -3, 0, 3, -13, 10, 4, 10], [0, -3, 5, 0, 0, 1, -5, 0], [14, 13, -1, 14, 0, 8, 1, 0], [0, 22, 0, -6, 4, 18, 3, 18], [6, -3, 9, 6, 0, -22, -9, 0], [0, -10, 0, -20, -5, -5, 10, -5], [-4, 0, 0, 4, 20, 0, 0, -10], [-4, -27, 4, -4, 0, -8, -4, 0], [-21, 8, 5, 0, 6, 14, 0, -14], [0, -22, 0, 33, -17, -5, -18, -5]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_975_n_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_975_2_n_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_975_2_n_o(:prec:=8)
    chi := MakeCharacter_975_n();
    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_975_2_n_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_975_2_n_o( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_975_n();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<2,R![49, -84, 72, -18, 18, -24, 18, -6, 1]>,<7,R![2401, 392, 32, -910, 882, -384, 98, -14, 1]>,<11,R![25, 30, 18, -92, 134, -54, 8, 4, 1]>,<37,R![1444, 456, 72, -68, 68, 12, 2, -2, 1]>],Snew);
    return Vf;
end function;