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A023902 Theta series of A_11 lattice. 13
1, 132, 2970, 19800, 66462, 194832, 420684, 881760, 1511730, 2770284, 4134240, 6754968, 9491130, 14310120, 18773964, 27609648, 34253142, 47864520, 58862870, 78974808, 93470652 (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

Table of n, a(n) for n=0..20.

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-Fran├žois 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.

STATUS

approved

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Last modified April 21 04:56 EDT 2019. Contains 322310 sequences. (Running on oeis4.)