A107501 Theta series of quadratic form with Gram matrix [ 6, 3, 2, 2; 3, 8, 1, 1; 2, 1, 18, 5; 2, 1, 5, 44].

1, 0, 0, 2, 4, 0, 0, 0, 0, 2, 6, 0, 6, 2, 6, 0, 8, 2, 0, 0, 0, 0, 14, 6, 0, 10, 6, 12, 0, 8, 20, 0, 0, 0, 0, 12, 24, 0, 22, 8, 28, 0, 26, 14, 0, 0, 0, 0, 36, 16, 0, 24, 14, 22, 0, 22, 30, 0, 0, 0, 0, 20, 34, 0, 30, 12, 36, 0, 32, 30, 0, 0, 0, 0, 26, 30, 0, 20

Offset

0,4

Comments

G.f. is theta_5 in the Parry 1979 reference on page 166. This theta series is an element of the space of modular forms on Gamma_0(169) of weight 2 and dimension 21. - Andy Huchala, May 13 2023

Links

Andy Huchala, Table of n, a(n) for n = 0..20000

W. R. Parry, A negative result on the representation of modular forms by theta series, J. Reine Angew. Math., 310 (1979), 151-170.

Example

G.f. = 1 + 2*q^6 + 4*q^8 + 2*q^18 + 6*q^20 + ...

Prog

(Magma)
prec := 90;
ls := [[6, 3, 2, 2], [3, 8, 1, 1], [2, 1, 18, 5], [2, 1, 5, 44]];
S := Matrix(ls);
L := LatticeWithGram(S);
M := ThetaSeriesModularFormSpace(L);
B := Basis(M, prec);
T<q> := ThetaSeries(L, 48);
coeffs := [Coefficients(T)[2*i-1] : i in [1..23]];
Coefficients(&+[coeffs[i]*B[i] :i in [1..13]]+&+[coeffs[i+1]*B[i] :i in [14..19]] + coeffs[22]*B[20] + coeffs[23]*B[21]); // Andy Huchala, May 13 2023

Crossrefs

Cf. A107498, A107499, A107500, A107502, A107503, A107504, A107505.

Sequence in context: A266296 A028573 A138758 * A126732 A371648 A347679

Adjacent sequences: A107498 A107499 A107500 * A107502 A107503 A107504

Keyword

nonn

Author

N. J. A. Sloane, May 28 2005

Extensions

Name clarified and more terms from Andy Huchala, May 13 2023

Status

approved