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 A343787 #7 Apr 29 2021 18:49:11
%S A343787 1,1,3,13,74,531,4563,45753,524345,6760039,96837333,1525909903,
%T A343787 26230304235,488472319271,9796281435125,210496933103743,
%U A343787 4824574494068495,117490079786298641,3029472152485535343,82454398253005541089,2362311059301928969755,71063998308414194250901
%N A343787 Number of ordered partitions of an n-set without blocks of size 4.
%F A343787 E.g.f.: 1 / (2 + x^4/4! - exp(x)).
%p A343787 a:= proc(n) option remember; `if`(n=0, 1, add(
%p A343787 `if`(j=4, 0, a(n-j)*binomial(n, j)), j=1..n))
%p A343787 end:
%p A343787 seq(a(n), n=0..21); # _Alois P. Heinz_, Apr 29 2021
%t A343787 nmax = 21; CoefficientList[Series[1/(2 + x^4/4! - Exp[x]), {x, 0, nmax}], x] Range[0, nmax]!
%t A343787 a[n_] := a[n] = If[n == 0, 1, Sum[If[k == 4, 0, Binomial[n, k] a[n - k]], {k, 1, n}]]; Table[a[n], {n, 0, 21}]
%Y A343787 Cf. A000670, A032032, A337058, A337059, A343664, A343788, A343789, A343790, A343791, A343792, A343793.
%K A343787 nonn
%O A343787 0,3
%A A343787 _Ilya Gutkovskiy_, Apr 29 2021