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 A361153 #3 Mar 03 2023 23:35:11 %S A361153 0,1,1,3,20,9731608032706560018 %N A361153 a(0)=0, a(1)=1; thereafter a(n) = (n-1)*a(n-1)! + (n-2)*a(n-2)!. %C A361153 The next term is too large to include. %C A361153 There is a suggestion that this is mentioned in Kenneth H. Rosen's book "Discrete Mathematics and Its Applications". It would be nice to have a precise reference, including edition, date, and page number. %Y A361153 Cf. A000045, A005604, A114045. %K A361153 nonn %O A361153 0,4 %A A361153 _N. J. A. Sloane_, Mar 03 2023, following a suggestion from _Akshat Kadia_, Feb 2023