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 A295257 #12 Nov 19 2017 02:06:45
%S A295257 1,1,4,32,368,5656,109024,2533712,68995328,2155513216,76014982144,
%T A295257 2987332904192,129473128921088,6135478762187776,315609465774936064,
%U A295257 17515027337549545472,1043104219010147483648,66358462250378681614336,4491141928841064201846784,322219449242531127348887552
%N A295257 Expansion of e.g.f. cot(x)*(1 - sqrt(1 - 4*tan(x)))/2.
%H A295257 Robert Israel, <a href="/A295257/b295257.txt">Table of n, a(n) for n = 0..365</a>
%F A295257 E.g.f.: 1/(1 - tan(x)/(1 - tan(x)/(1 - tan(x)/(1 - tan(x)/(1 - ...))))), a continued fraction.
%F A295257 a(n) ~ sqrt(17/2) * n^(n-1) / (exp(n) * (arctan(1/4))^(n-1/2)). - _Vaclav Kotesovec_, Nov 18 2017
%p A295257 S:= series(cot(x)*(1 - sqrt(1 - 4*tan(x)))/2, x, 32):
%p A295257 seq(n!*coeff(S,x,n),n=0..30); # _Robert Israel_, Nov 18 2017
%t A295257 nmax = 19; CoefficientList[Series[Cot[x] (1 - Sqrt[1 - 4 Tan[x]])/2, {x, 0, nmax}], x] Range[0, nmax]!
%t A295257 nmax = 19; CoefficientList[Series[1/(1 + ContinuedFractionK[-Tan[x], 1, {k, 1, nmax}]), {x, 0, nmax}], x] Range[0, nmax]!
%Y A295257 Cf. A000108, A195727, A295237, A295254, A295255, A295256, A295258.
%K A295257 nonn
%O A295257 0,3
%A A295257 _Ilya Gutkovskiy_, Nov 18 2017