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 A305708 #6 Mar 27 2019 03:53:00
%S A305708 1,-1,1,1,-11,43,-83,-275,3833,-21561,51369,375593,-5860147,40452371,
%T A305708 -101676235,-1409619211,23912208945,-189650997937,454996127889,
%U A305708 11250036170129,-204691511497499,1799897065507003,-3741969787709699,-164548323889940675,3183842522596250537,-30356999697044585833
%N A305708 Expansion of e.g.f. exp(cos(x)/exp(x) - 1).
%e A305708 exp(cos(x)/exp(x) - 1) = 1 - x + x^2/2! + x^3/3! - 11*x^4/4! + 43*x^5/5! - 83*x^6/6! - 275*x^7/7! + ...
%p A305708 a:=series(exp(cos(x)/exp(x)-1),x=0,26): seq(n!*coeff(a,x,n),n=0..25); # _Paolo P. Lava_, Mar 26 2019
%t A305708 nmax = 25; CoefficientList[Series[Exp[Cos[x]/Exp[x] - 1], {x, 0, nmax}], x] Range[0, nmax]!
%t A305708 a[n_] := a[n] = Sum[Re[(-1 - I)^k] Binomial[n - 1, k - 1] a[n - k], {k, 1, n}]; a[0] = 1; Table[a[n], {n, 0, 25}]
%Y A305708 Cf. A004211, A009116, A009216, A009235, A009255, A009276, A146559, A155585.
%K A305708 sign
%O A305708 0,5
%A A305708 _Ilya Gutkovskiy_, Jun 08 2018