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A015158
Theta series of 17-dimensional lattice Q_17(6).
8
1, 0, 2040, 41956, 362406, 1933920, 7591792, 24124428, 65640978, 158815904, 350243520, 715382916, 1373241708, 2505490464, 4367865216, 7321237204, 11884992774, 18736213536, 28751284680, 43126730772, 63361584408, 91360506752, 129562966320, 180742158696, 248590240202, 337956307872
OFFSET
0,3
LINKS
J. H. Conway and N. J. A. Sloane, Low-Dimensional Lattices II: Subgroups of GL(n,Z), Proc. Royal Soc. London, A 419 (1988), 29-68.
Gheorghe Coserea, Gram matrix.
G. Nebe and N. J. A. Sloane, Home page for this lattice
W. Plesken, Finite Unimodular Groups of Prime Degree and Circulants, J. Algebra, vol. 97 (1985), pp. 286-312.
EXAMPLE
1 + 2040*q^4 + 41956*q^6 + 362406*q^8 + 1933920*q^10 + 7591792*q^12 + 24124428*q^14 + 65640978*q^16 + 158815904*q^18 + 350243520*q^20 + 715382916*q^22 + 1373241708*q^24 + 2505490464*q^26 + 4367865216*q^28 + 7321237204*q^30 + ...
PROG
(PARI) \\ system("wget https://oeis.org/A015158/a015158.txt");
g = matconcat(read("a015158.txt")~);
seq(N, g, flag=0) = concat(1, 2*Vec(qfrep(g, N, flag)));
seq(10, g, 1) \\ Gheorghe Coserea, Nov 28 2018
(PARI)
GramMatrix()={my(p=[4, 2, 1, 1, 1, 0, -1, -2, -1, -1, -2, -1, 0, 1, 1, 1, 2]); matrix(#p, #p, i, j, p[(i-j) %#p + 1])}
a(n)={if(n==0, 1, 2*qfrep(GramMatrix(), n, 1)[n])} \\ Andrew Howroyd, Nov 29 2018
KEYWORD
nonn
EXTENSIONS
More terms from Gheorghe Coserea, Nov 29 2018
STATUS
approved