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 A367749 #11 Nov 29 2023 11:40:55
%S A367749 1,1,3,13,73,501,4051,37633,394353,4777993,62569891,893927541,
%T A367749 13827333433,234241234813,4212828738483,80727388033321,
%U A367749 1641227208417121,35581993575319953,810641581182744643,19416795485684156893,487647253209539939241
%N A367749 E.g.f. satisfies A(x) = exp(x * (1 + x + x^2 + x^3) * A(x^4)).
%F A367749 a(0) = 1; a(n) = (n-1)! * Sum_{k=0..n-1} (k+1) * a(floor(k/4)) * a(n-1-k) / (floor(k/4)! * (n-1-k)!).
%o A367749 (PARI) a_vector(n) = my(v=vector(n+1)); v[1]=1; for(i=1, n, v[i+1]=(i-1)!*sum(j=0, i-1, (j+1)*v[j\4+1]*v[i-j]/((j\4)!*(i-1-j)!))); v;
%Y A367749 Cf. A367747, A367748, A367751.
%Y A367749 Cf. A367653, A367720.
%K A367749 nonn
%O A367749 0,3
%A A367749 _Seiichi Manyama_, Nov 29 2023