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 A296544 #10 Mar 27 2019 10:04:29
%S A296544 1,0,-1,-3,-2,35,233,406,-6463,-72951,-234204,3454165,59129541,
%T A296544 299098488,-3983040037,-98320221991,-717243756890,8306677424447,
%U A296544 290745526287213,2888789037885782,-27716446593438731,-1389236305462658939,-18071746125863480076,133495439954224143065,10011730596035533451801
%N A296544 Expansion of e.g.f. sech(exp(x)-1).
%F A296544 E.g.f. 1/cosh(exp(x)-1).
%e A296544 sech(exp(x)-1) = 1 - x^2/2! - 3*x^3/3! - 2*x^4/4! + 35*x^5/5! + 233*x^6/6! + ...
%p A296544 a:=series(sech(exp(x)-1),x=0,25): seq(n!*coeff(a,x,n),n=0..24); # _Paolo P. Lava_, Mar 27 2019
%t A296544 nmax = 24; CoefficientList[Series[Sech[Exp[x] - 1], {x, 0, nmax}], x] Range[0, nmax]!
%Y A296544 Cf. A000364, A024430, A139134, A296543.
%K A296544 sign
%O A296544 0,4
%A A296544 _Ilya Gutkovskiy_, Dec 15 2017