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 A362319 #15 Feb 16 2025 08:34:05 %S A362319 1,1,1,1,1,121,865,3529,10753,27217,7318081,96720625,689990401, %T A362319 3508289929,14239793569,5933573525881,114415115802625, %U A362319 1165402803391009,8298505279241857,46355961619888993,26167218073714552321,663290722580370585625 %N A362319 a(n) = n! * Sum_{k=0..floor(n/5)} (n/5)^k / (k! * (n-5*k)!). %H A362319 Winston de Greef, <a href="/A362319/b362319.txt">Table of n, a(n) for n = 0..434</a> %H A362319 Eric Weisstein's World of Mathematics, <a href="https://mathworld.wolfram.com/LambertW-Function.html">Lambert W-Function</a>. %F A362319 a(n) = n! * [x^n] exp(x + n*x^5/5). %F A362319 E.g.f.: exp( ( -LambertW(-x^5) )^(1/5) ) / (1 + LambertW(-x^5)). %o A362319 (PARI) my(N=30, x='x+O('x^N)); Vec(serlaplace(exp((-lambertw(-x^5))^(1/5))/(1+lambertw(-x^5)))) %Y A362319 Cf. A277614, A362300, A362314. %K A362319 nonn %O A362319 0,6 %A A362319 _Seiichi Manyama_, Apr 16 2023