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%I #32 Jun 14 2018 16:42:05
%S 1,0,-1,-1,1,2,-1,3,-1,-1,-2,0,1,-2,4,-1,-3,-4,3,3,-2,10,-2,-6,-7,3,8,
%T -6,16,-4,-10,-12,4,9,-9,24,-6,-14,-17,8,14,-12,41,-9,-26,-30,15,30,
%U -21,64,-16,-35,-45,16,35,-33,90,-21,-55,-66,32,54,-44,140
%N McKay-Thompson series of class 21B for Monster.
%H Seiichi Manyama, <a href="/A058564/b058564.txt">Table of n, a(n) for n = -1..10000</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 1 + eta(q)*eta(q^3)/(eta(q^7)*eta(q^21)) in powers of q. - _G. C. Greubel_, Jun 14 2018
%e T21B = 1/q - q - q^2 + q^3 + 2*q^4 - q^5 + 3*q^6 - q^7 - q^8 - 2*q^9 + q^11 - ...
%t eta[q_]:= q^(1/24)*QPochhammer[q]; a:= CoefficientList[Series[q*(1 + (eta[q]*eta[q^3]/(eta[q^7]*eta[q^21]))), {q, 0, 60}], q]; Table[a[[n]], {n, 1, 70}] (* _G. C. Greubel_, Jun 14 2018 *)
%o (PARI) q='q+O('q^70); A = 1 + eta(q)*eta(q^3)/(eta(q^7)*eta(q^21))/q; Vec(A) \\ _G. C. Greubel_, Jun 14 2018
%Y Cf. A000521, A007240, A014708, A007241, A007267, A045478, etc.
%Y Cf. A226006 (same sequence except for n=0).
%K sign
%O -1,6
%A _N. J. A. Sloane_, Nov 27 2000
%E More terms from _Michel Marcus_, Feb 18 2014
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