
// Make newform 1470.2.a.d in Magma, downloaded from the LMFDB on 17 December 2025.
// To make the character of type GrpDrchElt, type "MakeCharacter_1470_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_1470_2_a_d();".
// 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_1470_2_a_d();".
// 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_1470_a();"
function MakeCharacter_1470_a()
    N := 1470;
    order := 1;
    char_gens := [491, 1177, 1081];
    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_1470_a_Hecke( : Kf := Kf)
    return MakeCharacter_1470_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]];
    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], [-1], [1], [0], [0], [-2], [-6], [4], [0], [-6], [-8], [2], [6], [-4], [0], [-6], [0], [10], [-4], [0], [-2], [8], [-12], [-18], [-2], [-18], [4], [-12], [-10], [-18], [20], [0], [6], [4], [-6], [8], [-2], [-4], [0], [-18], [24], [-14], [-24], [-22], [-6], [-8], [20], [-20], [12], [10], [-18], [24], [-2], [24], [18], [0], [6], [16], [2], [18], [28], [6], [-20], [0], [-2], [18], [-28], [26], [12], [10], [-6], [-24], [28], [26], [-4], [0], [-6], [22], [-6], [-26], [0], [-10], [0], [-26], [-8], [12], [-6], [26], [30], [-4], [36], [24], [-28], [24], [-4], [-24], [6], [-18], [-20], [-10], [-28], [18], [12], [18], [20], [-2], [12], [-30], [-24], [22], [4], [2], [30], [-44], [32], [-30], [4], [-24], [18], [48], [-14], [26], [6], [-12], [-44], [-6], [38], [0], [28], [22], [-52], [-24], [-40], [2], [-18], [-2], [-42], [4], [30], [-54], [4], [18], [20], [12], [-38], [-24], [46], [18], [4], [24], [2], [54], [-4], [0], [44], [-48], [-16], [6], [-26], [-18], [36], [6], [-4], [-24], [-42], [24], [-16], [-26], [2], [54], [48], [-14], [24], [50], [-56], [-18], [-52], [42], [28], [-14], [-52], [-48], [50], [-6], [0], [6], [2], [52], [26], [24], [22], [12], [-28], [30], [-36], [-6], [50], [-46], [-30], [24], [18], [-8], [22], [46], [0], [30], [40], [-12], [-30], [28], [-22], [-42], [44], [-60], [48], [-26], [20], [6], [24], [66], [-10], [40], [-30], [-52], [-12], [-58], [-6], [0], [-20], [48], [2], [-20], [-16], [18], [28], [24], [-50], [-54], [48], [48], [36], [-20], [-68], [38], [-6], [48], [-68], [-24], [-28], [-24], [-22], [-66], [-48], [-26], [-66], [-48], [-34], [28], [-42], [-2], [20], [-12], [58], [-26], [18], [-44], [-30], [-42], [-76], [-6], [34], [20], [46], [-40], [-26], [52], [-36], [38], [-22], [0], [-72], [-40], [72], [10], [4], [24], [-46], [42], [-8], [-66], [-30], [-60], [-66], [0], [26], [-18], [-56], [-42], [0], [28], [-50], [-78], [80], [12], [68], [-46], [-12], [-14], [48], [74], [-72], [66], [-54], [-28], [-72], [-26], [72], [24], [70], [-30], [-44], [2], [54], [-4], [-66], [-2], [20], [-44], [48], [-6], [62], [66], [88], [-60], [-52], [-36], [-34], [42], [-74], [-20], [74], [78], [78], [-40], [18], [24], [-38], [-4], [72], [-42], [-20], [-70], [42], [28], [14], [66], [48], [48], [-66], [-48], [-70], [-42], [0], [0], [-92], [-22], [30], [-52], [26], [-24], [-44], [-48], [-78], [40], [-22], [-24], [48], [46], [-42], [-26], [-18], [6], [92], [-42], [-68], [48], [8], [94], [92], [24], [2], [6], [-48], [52], [24], [-22], [-32], [-42], [20], [-54], [-14], [30], [-28], [-54], [30], [16], [74], [-6], [4], [48], [-2], [-54], [-60], [44], [2], [6], [-96], [-92], [-78], [-96], [-78], [-26], [-48], [72], [-2], [78], [-84], [-6], [-20], [24]];
    aps := ConvertToHeckeField(raw_aps);
    chi := MakeCharacter_1470_a_Hecke( : Kf := Universe(aps));
    return ExtendMultiplicatively(weight, aps, chi);
end function;


// To make the newform (type ModFrm), type "MakeNewformModFrm_1470_2_a_d();".
// 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_1470_2_a_d(:prec:=1)
    chi := MakeCharacter_1470_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_1470_2_a_d();".
// 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_1470_2_a_d( : sign := -1)
    R<x> := PolynomialRing(Rationals());
    chi := MakeCharacter_1470_a();
    // SetVerbose("ModularSymbols", true);
    Snew := NewSubspace(CuspidalSubspace(ModularSymbols(chi,2,sign)));
    Vf := Kernel([<11,R![0, 1]>,<13,R![2, 1]>,<17,R![6, 1]>,<19,R![-4, 1]>,<31,R![8, 1]>],Snew);
    return Vf;
end function;