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 A344495 #15 Jun 05 2021 05:17:19 %S A344495 1,2,6,27,112,585,3516,24661,197296,1775745,17757460,195332181, %T A344495 2343986184,30471820561,426605487868,6399082318245,102385317091936, %U A344495 1740550390563201,31329907030137636,595268233572615445,11905364671452308920,250012658100498487761,5500278478210966730764 %N A344495 a(0)=1; for n>0 a(n)=(a(n-1) + n) * n if n is odd, a(n-1)*n + n otherwise. %F A344495 a(n) ~ n! * (1 + 3*exp(1)/2 - exp(-1)/2). - _Vaclav Kotesovec_, Jun 05 2021 %e A344495 a(0) = 1; %e A344495 a(1) = (a(0)+1)*1 = (1+1)*1 = 2 ; %e A344495 a(2) = a(1)*2+2 = (2*2)+2 = 6 ; %e A344495 a(3) = (a(2)+3)*3 = (6+3)*3 = 9 ; %p A344495 a:= proc(n) a(n):= n*a(n-1) + n^(1+(n mod 2)) end: a(0):= 1: %p A344495 seq(a(n), n=0..22); # _Alois P. Heinz_, May 21 2021 %t A344495 a[0] = 1; a[n_] := a[n] = n*(a[n - 1] + If[OddQ[n], n, 1]); Array[a, 30, 0] (* _Amiram Eldar_, May 21 2021 *) %Y A344495 Cf. A344262. %K A344495 nonn,easy %O A344495 0,2 %A A344495 _Amrit Awasthi_, May 21 2021