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 A215096 #16 Oct 01 2024 15:45:10
%S A215096 0,1,2,5,22,115,698,4925,39622,357955,3589178,39558845,475412422,
%T A215096 6187461955,86702878778,1301486906045,20836087009222,354385941189955,
%U A215096 6381537618718778,121290714467642045,2426520470557921222,50969651457241797955,1121574207307049758778
%N A215096 a(0)=0, a(1)=1, a(n) = n! - a(n-2).
%F A215096 D-finite with recurrence a(n) -n*a(n-1) +a(n-2) -n*a(n-3)=0. - _R. J. Mathar_, Jun 04 2021
%p A215096 a:= proc(n) a(n):= `if`(n<2, n, n! - a(n-2)) end:
%p A215096 seq(a(n), n=0..23); # _Alois P. Heinz_, Jun 04 2021
%t A215096 nxt[{n_,a_,b_}]:={n+1,b,(n+1)!-a}; NestList[nxt,{1,0,1},30][[;;,2]] (* _Harvey P. Dale_, Feb 15 2024 *)
%o A215096 (Python)
%o A215096 prpr = 0
%o A215096 prev = f = 1
%o A215096 for n in range(2, 33):
%o A215096 print(prpr, end=', ')
%o A215096 f *= n
%o A215096 curr = f - prpr
%o A215096 prpr = prev
%o A215096 prev = curr
%Y A215096 Cf. A000142.
%Y A215096 Cf. A005165: a(0) = 0, a(n) = n! - a(n-1).
%K A215096 nonn
%O A215096 0,3
%A A215096 _Alex Ratushnyak_, Aug 03 2012