%I #13 Jun 25 2018 22:52:25
%S 1,2,0,0,0,0,-2,4,0,0,0,0,1,6,0,0,0,0,-2,12,0,0,0,0,4,18,0,0,0,0,-4,
%T 28,0,0,0,0,5,44,0,0,0,0,-6,64,0,0,0,0,9,92,0,0,0,0,-12,132,0,0,0,0,
%U 13,186,0,0,0,0,-16,256,0,0,0,0,21,352,0,0,0,0,-26,476,0,0,0,0,29,638,0,0,0,0,-36
%N McKay-Thompson series of class 24i for the Monster group.
%H G. C. Greubel, <a href="/A112166/b112166.txt">Table of n, a(n) for n = 0..2500</a>
%H D. Ford, J. McKay and S. P. Norton, <a href="http://dx.doi.org/10.1080/00927879408825127">More on replicable functions</a>, Comm. 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 A + 2*q/A, where A = q^(1/2)*(eta(q^6)/eta(q^12))^2, in powers of q. - _G. C. Greubel_, Jun 25 2018
%e T24i = 1/q + 2*q - 2*q^11 + 4*q^13 + q^23 + 6*q^25 - 2*q^35 + 12*q^37 + ...
%t eta[q_] := q^(1/24)*QPochhammer[q]; A:= q^(1/2)*(eta[q^6]/eta[q^12])^2; a:= CoefficientList[Series[A + 2*q/A, {q, 0, 60}], q]; Table[a[[n]], {n, 1, 50}] (* _G. C. Greubel_, Jun 25 2018 *)
%o (PARI) q='q+O('q^80); A = (eta(q^6)/eta(q^12))^2; Vec(A + 2*q/A) \\ _G. C. Greubel_, Jun 25 2018
%K sign
%O 0,2
%A _Michael Somos_, Aug 28 2005