
// Make newform 3150.2.a.g in Magma, downloaded from the LMFDB on 19 April 2024.
// To make the character of type GrpDrchElt, type "MakeCharacter_3150_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_3150_2_a_g();".
// 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_3150_2_a_g();".
// 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
        Kf := Rationals();
    end if;
    return [Kf!elt[1] : elt in input];
end function;


// To make the character of type GrpDrchElt, type "MakeCharacter_3150_a();"
function MakeCharacter_3150_a()
    N := 3150;
    order := 1;
    char_gens := [2801, 127, 451];
    v := [1, 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_3150_a_Hecke(Kf)
    return MakeCharacter_3150_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 := [[-1], [0], [0], [-1], [0], [-2], [0], [2], [0], [-6], [8], [4], [-6], [-2], [-6], [6], [-12], [8], [-2], [-6], [-2], [-16], [0], [-6], [10], [-6], [-8], [-12], [-10], [18], [16], [12], [-18], [-10], [-18], [8], [-14], [22], [-18], [-6], [12], [-16], [18], [-14], [6], [-4], [8], [-8], [-12], [20], [-6], [6], [2], [-12], [-12], [-12], [-30], [8], [-32], [0], [-20], [30], [4], [12], [-26], [18], [8], [-14], [-12], [-4], [-36], [6], [-8], [4], [8], [-6], [30], [22], [0], [2], [12], [-10], [-6], [-14], [8], [-36], [36], [-26], [-30], [4], [24], [-36], [16], [12], [-16], [6], [6], [18], [16], [2], [22], [18], [-12], [-24], [-4], [-2], [36], [-24], [42], [-22], [40], [28], [18], [-46], [32], [12], [-32], [42], [18], [48], [-40], [10], [18], [36], [26], [-30], [26], [-36], [40], [22], [-16], [48], [32], [-20], [54], [14], [-42], [4], [18], [48], [38], [-30], [28], [12], [20], [48], [-26], [-12], [2], [-36], [-32], [30], [-2], [-18], [-2], [-30], [32], [30], [-38], [42], [-12], [-6], [-8], [-36], [-6], [-54], [-16], [46], [38], [-6], [-24], [-40], [54], [-62], [-16], [30], [20], [6], [-32], [20], [-44], [12], [28], [-48], [60], [-42], [4], [64], [14], [-36], [34], [-12], [56], [-6], [12], [-24], [-58], [40], [-12], [-6], [6], [-52], [-38], [14], [-12], [-42], [-16], [-12], [36], [-46], [10], [-6], [16], [24], [-72], [-34], [40], [66], [-60], [66], [-22], [20], [-48], [52], [-60], [2], [-36], [-30], [-8], [-36], [40], [2], [8], [-12], [-20], [6], [-22], [6], [36], [72], [12], [2], [-32], [50], [24], [-36], [16], [12], [32], [36], [-32], [-30], [12], [-58], [-18], [-12], [-34], [-44], [6], [-38], [-44], [-60], [80], [-38], [-60], [26], [6], [-54], [58], [54], [-40], [82], [-26], [-16], [-50], [16], [-12], [74], [-10], [-36], [18], [32], [-42], [-76], [-80], [-42], [-26], [30], [-16], [6], [-42], [-12], [66], [-12], [40], [30], [80], [30], [-60], [52], [-38], [18], [-16], [-36], [-28], [-26], [12], [32], [66], [52], [42], [-54], [-24], [-50], [-36], [14], [36], [6], [-14], [-60], [26], [58], [30], [-8], [-18], [50], [-76], [40], [12], [-66], [14], [-30], [-28], [-72], [-4], [48], [-70], [24], [-10], [-56], [-44], [18], [54], [-64], [30], [60], [44], [82], [-48], [-42], [14], [46], [18], [64], [2], [-12], [60], [60], [66], [-36], [-44], [-18], [60], [-24], [4], [46], [54], [4], [50], [0], [-70], [-60], [66], [-40], [88], [60], [-18], [-86], [42], [10], [-66], [18], [64], [30], [-34], [66], [32], [70], [-2], [-90], [-94], [42], [72], [-68], [90], [22], [-4], [-66], [56], [-18], [68], [18], [-68], [48], [90], [-52], [-8], [-12], [-92], [-12], [-62], [42], [-12], [20], [-86], [78], [54], [-80], [12], [-90], [6], [22], [96], [36], [-74], [54], [36], [-36], [-34], [96]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_3150_a_Hecke(Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_3150_2_a_g();".
// 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_3150_2_a_g(:prec:=1)
    chi := MakeCharacter_3150_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(2999) - 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_3150_2_a_g();".
// 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_3150_2_a_g( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_3150_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<11,R![0, 1]>,<13,R![2, 1]>,<17,R![0, 1]>,<19,R![-2, 1]>,<29,R![6, 1]>],Snew);
    return Vf;
end function;