This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A296680 #7 Dec 18 2017 22:51:34
%S A296680 1,3,53,2359,198953,27412011,5625656541,1613676694239,617477049181521,
%T A296680 304167421243513683,187546541676182230149,141512355477854459198343,
%U A296680 128265950128144233675269241,137512081213377707268891639675,172108297920263623816775456321325
%N A296680 Expansion of e.g.f. arcsin(arctanh(x)) (odd powers only).
%H A296680 Robert Israel, <a href="/A296680/b296680.txt">Table of n, a(n) for n = 0..215</a>
%F A296680 E.g.f.: arcsinh(arctan(x)) (odd powers only, absolute values).
%F A296680 E.g.f.: -i*log((i/2)*(log(1 + x) - log(1 - x)) + sqrt(1 - (log(1 + x) - log(1 - x))^2/4)), where i is the imaginary unit (odd powers only).
%e A296680 arcsin(arctanh(x)) = x/1! + 3*x^3/3! + 53*x^5/5! + 2359*x^7/7! + 198953*x^9/9! + 27412011*x^11/11! + ...
%p A296680 S:= series(arcsin(arctanh(x)),x,52):
%p A296680 seq(coeff(S,x,n)*n!,n=1..51,2); # _Robert Israel_, Dec 18 2017
%t A296680 nmax = 15; Table[(CoefficientList[Series[ArcSin[ArcTanh[x]], {x, 0, 2 nmax + 1}], x] Range[0, 2 nmax + 1]!)[[n]], {n, 2, 2 nmax, 2}]
%t A296680 nmax = 15; Table[(CoefficientList[Series[-I Log[(I/2) (Log[1 + x] - Log[1 - x]) + Sqrt[1 - (Log[1 + x] - Log[1 - x])^2/4]], {x, 0, 2 nmax + 1}], x] Range[0, 2 nmax + 1]!)[[n]], {n, 2, 2 nmax, 2}]
%Y A296680 Cf. A001818, A003717, A010050, A012134, A296464, A296466, A296679.
%K A296680 nonn
%O A296680 0,2
%A A296680 _Ilya Gutkovskiy_, Dec 18 2017