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 A023902 Theta series of A_11 lattice. 14
 1, 132, 2970, 19800, 66462, 194832, 420684, 881760, 1511730, 2770284, 4134240, 6754968, 9491130, 14310120, 18773964, 27609648, 34253142, 47864520, 58862870, 78974808, 93470652, 125490024, 143483340, 186539760, 214957644, 271553700, 304365600 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES J. H. Conway and N. J. A. Sloane, "Sphere Packings, Lattices and Groups", Springer-Verlag, p. 110. LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..1000 MATHEMATICA terms = 21; f[q_] = LatticeData["A11", "ThetaSeriesFunction"][-I Log[q] / Pi]; s = Series[f[q], {q, 0, 2 terms}]; CoefficientList[s, q^2][[1 ;; terms]] (* Jean-François Alcover, Jul 04 2017 *) PROG (PARI) theta3(k, n, prec, f, m)=f=polcyclo(n); 1+sum(m=1, sqrtint(prec), Mod(x^(m*k%n)+x^(m*(n-k)%n), f)*q^sqr(m))+O(q^(prec+1)) aaa(n, prec, k, m)=sum(k=0, n-1, theta3(k, n, prec)^n)/n/(1+2*sum(m=1, sqrtint(floor(prec/n)), q^(n*sqr(m)))+O(q^(prec+1))) doit(m, prec)=subst(lift(aaa(m+1, prec)), x, 0) \\ gives theta series of A_m to order "prec"; code from Robert.Harley(AT)inria.fr CROSSREFS Sequence in context: A220996 A254646 A242147 * A240270 A168180 A236260 Adjacent sequences: A023899 A023900 A023901 * A023903 A023904 A023905 KEYWORD nonn AUTHOR N. J. A. Sloane. EXTENSIONS More terms from Sean A. Irvine, Jun 12 2019 STATUS approved

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Last modified July 14 12:15 EDT 2024. Contains 374318 sequences. (Running on oeis4.)