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 A161395 a(n) = (n+1)*A000521(n)/24. 3

%I

%S 0,31,16407,2686720,144049995,4217886720,83300660150,1240173462528,

%T 14885664690645,150559082496000,1323516762410175,10343388600230400,

%U 73105955749759647,473586598163128320,2842005898548916470

%N a(n) = (n+1)*A000521(n)/24.

%C Comment from John McKay (mckay(AT)encs.concordia.ca), Jun 09 2009: This is in a paper by Lehmer from about 1945. It is related to the q-coefficients of j'/j. Added Oct 13 2010: Note j'/j = weight 2 on the modular group = E6/E4 = (1-504...)/(1+240...) = -1/1 mod 24 so j'+j == 0 (mod 24) so coefficient of q^n gives n*c(n) + c(n) = (n+1)c(n) == 0 (mod 24).

%H G. C. Greubel, <a href="/A161395/b161395.txt">Table of n, a(n) for n = -1..1000</a>

%F a(n) ~ exp(4*Pi*sqrt(n)) * n^(1/4) / (3 * 2^(7/2)). - _Vaclav Kotesovec_, Jun 09 2018

%t a[n_] := With[{tau = Log[q]/(2 Pi I)}, SeriesCoefficient[Series[1728 KleinInvariantJ[tau], {q, 0, n}], {q, 0, n}]]; Table[(n + 1) a[n]/24, {n, -1, 100}] (* _G. C. Greubel_, Feb 20 2017 *)

%K nonn

%O -1,2

%A _Alexander R. Povolotsky_, Jun 09 2009

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Last modified September 27 08:39 EDT 2021. Contains 347689 sequences. (Running on oeis4.)