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 A373684 #9 Jun 13 2024 08:15:49
%S A373684 1,1,1,7,49,181,1201,16171,122977,971209,16788961,206578351,
%T A373684 2094314641,40260673597,694617709969,9088535091091,187060085419201,
%U A373684 4109646055718161,68029103349383617,1498126927153125079,39199612737165358321,799248202624341298501
%N A373684 Expansion of e.g.f. exp(x / (1 - x^3)) / (1 - x^3).
%F A373684 a(n) = n! * Sum_{k=0..floor(n/3)} binomial(n-2*k,k)/(n-3*k)!.
%F A373684 a(n) == 1 (mod 6).
%o A373684 (PARI) a(n) = n!*sum(k=0, n\3, binomial(n-2*k, k)/(n-3*k)!);
%Y A373684 Cf. A002720, A373683.
%Y A373684 Cf. A293493.
%K A373684 nonn
%O A373684 0,4
%A A373684 _Seiichi Manyama_, Jun 13 2024