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 A099953 #25 Apr 04 2017 04:27:37
%S A099953 0,1,4,19,124,1069,11464,146599,2173624,36633049,691362124,
%T A099953 14440672699,330674815924,8236528396549,221694575073424,
%U A099953 6411977928702799,198310761891213424,6530970632654064049,228174066109353835924
%N A099953 a(n) = A076795(n) - 1.
%F A099953 a(n) = (2*n-2)*a(n-1)-(2*n-3)*a(n-2) with a(1)=0, a(2)=1. - _Emeric Deutsch_ and _Ira M. Gessel_, Dec 19 2004
%F A099953 G.f.: A(x)=x/(1-x)/(U(0)-x), where U(k)= (2*k+1)*x + 1 - (2*k+3)*x/U(k+1); (continued fraction Euler's 1st kind, 1-step ). - _Sergei N. Gladkovskii_, Jun 27 2012
%p A099953 a[1]:=0: a[2]:=1: for n from 3 to 30 do a[n]:=(2*n-2)*a[n-1]-(2*n-3)*a[n-2] od:seq(a[j],j=1..18); # _Emeric Deutsch_, Dec 20 2004
%t A099953 s = 0; lst = {s}; Do[s += n!!; AppendTo[lst, s], {n, 1, 32, 2}]; lst (* _Zerinvary Lajos_, Jul 13 2009 *)
%Y A099953 Cf. A001147.
%K A099953 nonn,easy
%O A099953 1,3
%A A099953 _N. J. A. Sloane_, Nov 12 2004
%E A099953 More terms from _Emeric Deutsch_ and _Ira M. Gessel_, Dec 20 2004