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 A371046 #8 Mar 09 2024 08:16:24 %S A371046 1,0,0,6,24,60,1560,25410,242256,3508344,85882320,1724406750, %T A371046 32784999720,839182482996,24162605028744,659439484706730, %U A371046 19415319297457440,658935736181053680,23245444335085544736,835819877947421773494,32462532011236141677240 %N A371046 E.g.f. satisfies A(x) = 1 + x^3*A(x)^2*exp(x*A(x)). %F A371046 a(n) = n! * Sum_{k=0..floor(n/3)} k^(n-3*k) * binomial(n-k+1,k)/( (n-k+1)*(n-3*k)! ). %o A371046 (PARI) a(n) = n!*sum(k=0, n\3, k^(n-3*k)*binomial(n-k+1, k)/((n-k+1)*(n-3*k)!)); %Y A371046 Cf. A370985, A371019, A371044, A371045. %Y A371046 Cf. A365286. %K A371046 nonn %O A371046 0,4 %A A371046 _Seiichi Manyama_, Mar 09 2024