%I M4962 #25 Oct 09 2017 21:48:45
%S 1,0,15,-32,87,-192,343,-672,1290,-2176,3705,-6336,10214,-16320,25905,
%T -39936,61227,-92928,138160,-204576,300756,-435328,626727,-897408,
%U 1271205,-1790592,2508783,-3487424,4824825,-6641664,9083400,-12371904,16778784,-22630912,30407112,-40703040,54238342,-72018624
%N McKay-Thompson series of class 6C for Monster (and, apart from signs, of class 12A).
%C Apart from a(0) same as A045486 and A121666. [_Joerg Arndt_, Apr 09 2016]
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%H G. C. Greubel, <a href="/A007256/b007256.txt">Table of n, a(n) for n = -1..1000</a>
%H J. H. Conway and S. P. Norton, <a href="http://blms.oxfordjournals.org/content/11/3/308.extract">Monstrous Moonshine</a>, Bull. Lond. Math. Soc. 11 (1979) 308-339.
%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 J. McKay and H. Strauss, <a href="http://dx.doi.org/10.1080/00927879008823911">The q-series of monstrous moonshine and the decomposition of the head characters</a>, Comm. Algebra 18 (1990), no. 1, 253-278.
%H <a href="/index/Mat#McKay_Thompson">Index entries for McKay-Thompson series for Monster simple group</a>
%e T6C = 1/q + 15*q - 32*q^2 + 87*q^3 - 192*q^4 + 343*q^5 - 672*q^6 + ...
%t QP = QPochhammer; A007256[n_] := SeriesCoefficient[((QP[q]*(QP[q^3]) /(QP[q^2]*QP[q^6])))^6/q^1 + 6, {q, 0, n}]; Join[{1}, Table[A007256[n], {n, 0, 50}]] (* _G. C. Greubel_, Oct 09 2017 *)
%o (PARI) N=66; q='q+O('q^N); Vec( ((eta(q^1)*eta(q^3))/ (eta(q^2)*eta(q^6)))^6/q + 6 ) \\ _Joerg Arndt_, Apr 09 2016
%Y Cf. A045486.
%K sign
%O -1,3
%A _N. J. A. Sloane_