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%I #30 Dec 24 2018 09:11:39
%S 1,0,0,0,0,0,0,816,2040,0,0,20400,41956,0,0,236912,362406,0,0,1236240,
%T 1933920,0,0,5861328,7591792,0,0,17201280,24124428,0,0,55003296,
%U 65640978,0,0,120568080,158815904,0,0,307510960,350243520,0,0,564643440,715382916,0,0,1246785984,1373241708,0,0
%N Theta series of 17-dimensional lattice Q_17(6)^{+2}.
%H J. H. Conway and N. J. A. Sloane, <a href="https://www.jstor.org/stable/2398331">Low-Dimensional Lattices II: Subgroups of GL(n,Z)</a>, Proc. Royal Soc. London, A 419 (1988), 29-68.
%H Gheorghe Coserea, <a href="/A015159/a015159.txt">Gram matrix</a>.
%H G. Nebe and N. J. A. Sloane, <a href="http://www.math.rwth-aachen.de/~Gabriele.Nebe/LATTICES/Q1762.html">Home page for this lattice</a>
%H W. Plesken, <a href="https://core.ac.uk/download/pdf/82549703.pdf">Finite Unimodular Groups of Prime Degree and Circulants</a>, J. Algebra, vol. 97 (1985), pp. 286-312.
%e 1 + 816*q^7 + 2040*q^8 + 20400*q^11 + 41956*q^12 + 236912*q^15 + 362406*q^16 + 1236240*q^19 + 1933920*q^20 + 5861328*q^23 + 7591792*q^24 + 17201280*q^27 + 24124428*q^28 + ...
%o (PARI) \\ system("wget https://oeis.org/A015159/a015159.txt");
%o g = matconcat(read("a015159.txt")~);
%o seq(N, g, flag=0) = concat(1, 2*Vec(qfrep(g, N, flag)));
%o seq(20, g) \\ _Gheorghe Coserea_, Nov 28 2018
%o (PARI)
%o GramMatrix()={my(p=[7, -1, -3, 1, 1, -1, 1, 3, -3, -3, 3, 1, -1, 1, 1, -3, -1]); matrix(#p, #p, i, j, p[(i-j) %#p + 1])}
%o a(n)={if(n==0, 1, 2*qfrep(GramMatrix(), n, 0)[n])} \\ _Andrew Howroyd_, Nov 29 2018
%Y Cf. A015158, A015160, A015161, A015162, A015163, A015164, A015165.
%K nonn
%O 0,8
%A _N. J. A. Sloane_
%E More terms from _Gheorghe Coserea_, Nov 28 2018
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