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 A296730 #11 Dec 19 2017 18:33:13
%S A296730 1,-1,-31,-337,24705,2451679,-17936543,-42895630065,-5396647099903,
%T A296730 1239561882325439,708575518706816481,37448619025871342959,
%U A296730 -113842057082636742446975,-52054011876398495316250977,16226448322449614832534708065,31975745831751940004484917311439
%N A296730 Expansion of e.g.f. arctanh(x*cos(x)) (odd powers only).
%F A296730 a(n) = (2*n+1)! * [x^(2*n+1)] arctanh(x*cos(x)).
%e A296730 arctanh(x*cos(x)) = x/1! - x^3/3! - 31*x^5/5! - 337*x^7/7! + 24705*x^9/9! + ...
%t A296730 nmax = 16; Table[(CoefficientList[Series[ArcTanh[x Cos[x]], {x, 0, 2 nmax + 1}], x] Range[0, 2 nmax + 1]!)[[n]], {n, 2, 2 nmax, 2}]
%o A296730 (PARI) first(n) = x='x+O('x^(2*n)); vecextract(Vec(serlaplace(atanh(x*cos(x)))), (4^n - 1)/3) \\ _Iain Fox_, Dec 19 2017
%Y A296730 Cf. A000364, A009015, A009016, A009446, A009447, A009633, A009634, A010050, A012494, A191512, A296465, A296467, A296728, A296729, A296731, A296740.
%K A296730 sign
%O A296730 0,3
%A A296730 _Ilya Gutkovskiy_, Dec 19 2017