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%I #24 Jun 28 2018 04:41:56
%S 1,2,3,6,9,14,22,30,42,60,81,110,148,194,256,336,433,556,713,904,1144,
%T 1440,1798,2242,2784,3438,4234,5196,6353,7748,9419,11414,13796,16636,
%U 20004,23996,28722,34296,40869,48604,57678,68318,80779,95332,112313,132104,155117,181856,212890
%N McKay-Thompson series of class 28D for Monster.
%H G. C. Greubel, <a href="/A058609/b058609.txt">Table of n, a(n) for n = -1..1000</a>
%H D. Ford, J. McKay and S. P. Norton, <a href="http://dx.doi.org/10.1080/00927879408825127">More on replicable functions</a>, Commun. Algebra 22, No. 13, 5175-5193 (1994).
%H <a href="/index/Mat#McKay_Thompson">Index entries for McKay-Thompson series for Monster simple group</a>
%F Expansion of q^(1/2)*((eta(q^2)*eta(q^7))/(eta(q)*eta(q^14)))^2 in powers of q. - _G. C. Greubel_, Jun 18 2018
%F a(n) ~ exp(2*Pi*sqrt(n/7)) / (2 * 7^(1/4) * n^(3/4)). - _Vaclav Kotesovec_, Jun 28 2018
%e T28D = 1/q + 2*q + 3*q^3 + 6*q^5 + 9*q^7 + 14*q^9 + 22*q^11 + 30*q^13 + ...
%t eta[q_]:= q^(1/24)*QPochhammer[q]; e28D:= q^(1/2)*((eta[q^2]*eta[q^7])/(eta[q]*eta[q^14]))^2; a[n_] := SeriesCoefficient[e28D , {q, 0, n}]; Table[a[n], {n, 0, 50}] (* _G. C. Greubel_, Feb 18 2018 *)
%o (PARI) q='q+O('q^50); A = ((eta(q^2)*eta(q^7))/(eta(q)*eta(q^14)))^2; Vec(A) \\ _G. C. Greubel_, Jun 18 2018
%Y Cf. A000521, A007240, A014708, A007241, A007267, A045478, etc.
%K nonn
%O -1,2
%A _N. J. A. Sloane_, Nov 27 2000
%E Terms a(12) onward added by _G. C. Greubel_, Feb 18 2018
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