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 A291286 #7 Aug 27 2017 13:42:49 %S A291286 1,2,4,16,88,632,5552,57824,695776,9500128,145097152,2451080192, %T A291286 45373649024,913400022656,19865889564928,464227147597312, %U A291286 11599471170191872,308605525316616704,8709955613991289856,259922447412719218688,8177253768239405504512 %N A291286 a(0)=1, a(1)=2, thereafter a(n) = n*a(n-1)+(n-1)*(n-2)*a(n-2). %p A291286 f:=proc(n) option remember; %p A291286 if n <= 1 then n+1 else %p A291286 n*f(n-1)+(n-1)*(n-2)*f(n-2); fi; end; %p A291286 [seq(f(n),n=0..40)]; %Y A291286 A244430 and A291287 have the same recurrence. %K A291286 nonn %O A291286 0,2 %A A291286 _N. J. A. Sloane_, Aug 27 2017