
// Make newform 450.2.p.a in Magma, downloaded from the LMFDB on 18 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_450_p();"
// To make the character of type GrpDrchElt with Codomain the HeckeField, type "MakeCharacter_450_p_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_450_2_p_a();".
// 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_450_2_p_a();".
// 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, 0, 0, 0, -1, 0, 0, 0, 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_450_p();"
function MakeCharacter_450_p()
    N := 450;
    order := 12;
    char_gens := [101, 127];
    v := [10, 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_450_p_Hecke();"
function MakeCharacter_450_p_Hecke(Kf)
    N := 450;
    order := 12;
    char_gens := [101, 127];
    char_values := [[1, 0, 0, 0, -1, 0, 0, 0], [0, 0, 0, 0, 0, 0, -1, 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, 0, 0, 0, 0, 0, 1], [-1, 0, -1, 0, 1, 1, 0, 0], [0, 0, 0, 0, 0, 0, 0, 0], [0, 0, 2, -2, 2, 0, -2, 1], [-4, -2, 0, 0, 2, 0, 0, 2], [0, -4, 0, 0, 0, 2, 0, 0], [1, 0, -2, -2, -2, 0, 1, 0], [0, 1, 0, -1, 0, 1, -4, 2], [0, 0, 0, 0, 0, -1, 0, 0], [0, -1, -1, 0, 0, 0, -1, -1], [2, 2, 0, -1, -2, -1, 0, -1], [3, 0, 0, 0, 0, 0, -3, 0], [1, 0, 0, -4, 1, -4, 0, 4], [0, -2, 0, 0, 0, 4, 0, 0], [0, 0, 0, 0, 0, 0, 0, 9], [-3, -2, -6, 0, 6, 2, 3, 0], [0, 0, -6, -1, 0, 1, 12, 1], [0, -1, 0, 2, 3, 2, 0, -1], [-1, 0, 1, -3, 1, 0, 0, -3], [2, -2, 0, 2, -4, 2, 0, 0], [2, -4, 0, 0, 0, -4, 2, 0], [0, 1, 0, 2, 0, -2, 0, -1], [-2, 3, -1, 0, 1, 0, -1, 0], [0, 2, -6, 2, 0, -2, 3, 0], [0, 0, -3, -8, -3, 0, 3, 4], [8, -4, 0, 0, -4, 0, 0, 4], [-2, 8, -2, 0, 2, -4, 0, 0], [5, 0, -10, 7, -10, 0, 5, 0], [0, 3, 0, -3, 0, 3, 13, 6], [4, 0, -4, 0, 4, 4, 8, 0], [-8, 0, 0, -5, 0, 0, 8, 10], [2, 0, 0, 5, 2, 5, 0, -5], [-8, 0, 4, 0, 4, 0, 4, -12], [0, 4, 8, 2, 0, -2, 0, 2], [0, 0, 5, 3, 0, -3, -10, -3], [0, -8, 0, 16, 2, 16, 0, -8], [-3, 0, 3, -6, 3, 0, 0, -6], [-2, 2, 0, 0, 0, 2, -2, 0], [4, 0, 4, 1, 4, 0, -8, -1], [4, -8, 2, 0, -2, 0, 2, 0], [0, -10, -4, -10, 0, 10, 2, 0], [-13, 1, 0, 1, 0, 1, 0, -2], [-12, 5, 0, 0, 6, 0, 0, -5], [0, 20, 0, 0, 0, -10, 0, 0], [4, 0, -8, 0, -8, 0, 4, 0], [0, 1, 0, -1, 0, 1, -6, 2], [-14, -4, 0, 2, 14, 2, 0, 2], [0, 5, -12, 0, 12, -10, 12, 0], [-4, 0, 2, 0, 2, 0, 2, -20], [0, -6, -9, -3, 0, 3, 0, -3], [1, -18, 2, 0, -2, 18, -1, 0], [0, 0, 0, 12, 0, -12, 0, -12], [0, 0, 0, 0, -19, 0, 0, 0], [4, 3, 0, -3, -8, -3, 0, 0], [9, 0, 9, 4, 9, 0, -18, -4], [-12, 2, -6, 0, 6, 0, -6, 0], [0, 7, -6, 7, 0, -7, 3, 0], [6, -9, 0, -9, 0, -9, 0, 18], [0, 0, -15, 8, -15, 0, 15, -4], [-10, 6, 0, 0, 5, 0, 0, -6], [11, -10, 11, 0, -11, 5, 0, 0], [-9, 0, 9, 0, -9, 0, -18, 0], [3, 0, 0, -3, 0, 0, -3, 6], [2, 0, 0, -17, 2, -17, 0, 17], [0, 2, -6, 0, 6, -4, 6, 0], [4, 0, -2, 0, -2, 0, -2, 6], [0, -1, 0, 2, 2, 2, 0, -1], [-12, 0, 12, 8, 12, 0, 0, 8], [-4, 0, -4, 14, -4, 0, 8, -14], [0, 9, -7, 18, 0, -18, 7, -9], [28, 0, 14, 0, -14, 0, 14, 0], [0, 5, 12, 5, 0, -5, -6, 0], [0, 0, 2, 8, 2, 0, -2, -4], [7, 12, 7, 0, -7, -6, 0, 0], [0, -3, 0, 3, 0, -3, 14, -6], [-4, 0, 4, 0, -4, -18, -8, 0], [0, -15, 9, 0, 0, 0, 9, -15], [-13, 0, 0, -2, 0, 0, 13, 4], [10, 0, 0, 6, 10, 6, 0, -6], [0, 4, -24, 2, 0, -2, 0, 2], [0, 0, -2, -6, 0, 6, 4, 6], [0, -2, 0, 4, 10, 4, 0, -2], [0, 11, 0, -11, 0, -11, 0, 0], [-11, 2, 0, 0, 0, 2, -11, 0], [0, 4, -20, 8, 0, -8, 20, -4], [2, -3, 1, 0, -1, 0, 1, 0], [0, -8, -12, -8, 0, 8, 6, 0], [0, 0, -3, 12, -3, 0, 3, -6], [30, -5, 0, 0, -15, 0, 0, 5], [-16, -12, -16, 0, 16, 6, 0, 0], [0, 0, 0, 4, 0, 0, 0, 0], [0, 5, 0, 0, 0, 0, 0, 5], [12, 0, 0, 0, 0, 0, -12, 0], [-8, 0, 0, 10, -8, 10, 0, -10], [0, -4, -4, -2, 0, 2, 0, -2], [-6, -9, -12, 0, 12, 9, 6, 0], [0, 0, 9, 17, 0, -17, -18, -17], [17, 0, 0, 0, -34, 0, 0, 0], [-3, 1, 0, 0, 0, 1, -3, 0], [1, -11, 0, -11, 0, -11, 0, 22], [0, 0, -9, -10, -9, 0, 9, 5], [-7, 0, 14, 6, 14, 0, -7, 0], [3, 0, -3, 0, 3, 27, 6, 0], [0, 16, 2, 0, 0, 0, 2, 16], [-32, 4, 0, -2, 32, -2, 0, -2], [17, 0, 0, 0, 0, 0, -17, 0], [-18, 0, 9, 0, 9, 0, 9, 9], [5, 2, 10, 0, -10, -2, -5, 0], [0, 0, -4, -19, 0, 19, 8, 19], [0, 6, 0, -12, -20, -12, 0, 6], [12, 0, -12, -3, -12, 0, 0, -3], [3, 8, 0, 0, 0, 8, 3, 0], [2, 0, 2, -12, 2, 0, -4, 12], [0, -15, 12, -30, 0, 30, -12, 15], [-8, -2, 0, -2, 0, -2, 0, 4], [6, -10, 0, 0, -3, 0, 0, 10], [-9, -22, -9, 0, 9, 11, 0, 0], [14, 0, -28, -1, -28, 0, 14, 0], [-1, 0, 1, 0, -1, 24, -2, 0], [0, -8, 0, 0, 0, 0, 0, -8], [16, 12, 0, -6, -16, -6, 0, -6], [0, -2, 14, 0, -14, 4, -14, 0], [16, 0, -8, 0, -8, 0, -8, 26], [8, 0, 16, 0, -16, 0, -8, 0], [0, 11, 0, -22, -6, -22, 0, 11], [-13, -1, 0, 1, 26, 1, 0, 0], [0, -3, -37, -6, 0, 6, 37, 3], [0, -23, 0, -23, 0, 23, 0, 0], [0, 0, 6, -46, 6, 0, -6, 23], [7, -28, 7, 0, -7, 14, 0, 0], [0, 11, 0, -11, 0, 11, -2, 22], [2, 0, -2, 0, 2, -5, 4, 0], [-6, 12, 0, -6, 6, -6, 0, -6], [0, 0, 0, 18, 0, 0, 0, -36], [-7, 0, 0, -4, -7, -4, 0, 4], [0, 12, 5, 6, 0, -6, 0, 6], [-8, 24, -16, 0, 16, -24, 8, 0], [-2, 0, 2, -4, 2, 0, 0, -4], [-4, 0, -4, 30, -4, 0, 8, -30], [0, 26, 20, 26, 0, -26, -10, 0], [2, 17, 0, 17, 0, 17, 0, -34], [-2, -17, 0, 0, 1, 0, 0, 17], [-16, -30, -16, 0, 16, 15, 0, 0], [17, 0, -34, 3, -34, 0, 17, 0], [0, 1, 0, -1, 0, 1, 13, 2], [0, 7, 6, 0, 0, 0, 6, 7], [0, 10, 14, 0, -14, -20, -14, 0], [-8, 0, 4, 0, 4, 0, 4, -6], [0, 20, -22, 10, 0, -10, 0, 10], [14, 5, 28, 0, -28, -5, -14, 0], [18, 0, -18, 10, -18, 0, 0, 10], [-1, -40, 0, 40, 2, 40, 0, 0], [17, 19, 0, 0, 0, 19, 17, 0], [-4, 0, -4, -18, -4, 0, 8, 18], [0, 0, 1, 6, 1, 0, -1, -3], [0, 5, 0, 0, 0, 0, 0, -5], [0, -3, 0, 3, 0, -3, -20, -6], [0, 2, 26, 0, 0, 0, 26, 2], [8, 0, 0, 4, 0, 0, -8, -8], [11, 0, 0, -9, 11, -9, 0, 9], [-18, 0, 9, 0, 9, 0, 9, 19], [-4, -18, -8, 0, 8, 18, 4, 0], [-32, 0, 32, 3, 32, 0, 0, 3], [8, 25, 0, -25, -16, -25, 0, 0], [-10, 0, -10, -18, -10, 0, 20, 18], [-8, -37, -4, 0, 4, 0, -4, 0], [-20, -15, 0, -15, 0, -15, 0, 30], [0, 0, -17, -20, -17, 0, 17, 10]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_450_p_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_450_2_p_a();".
// 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_450_2_p_a(:prec:=8)
    chi := MakeCharacter_450_p();
    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_450_2_p_a();".
// 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_450_2_p_a( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_450_p();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<7,R![625, -1000, 800, -880, 679, -176, 32, -8, 1]>,<11,R![16, 48, 52, 12, 1]>],Snew);
    return Vf;
end function;