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 A190875 #17 Sep 06 2025 01:39:02
%S A190875 1,1,1,1,25,121,361,841,21841,184465,912241,3334321,89824681,
%T A190875 1063799881,7325422105,36454050361,1017339566881,15314809967521,
%U A190875 134865698721121,848781820990945,24508030788375481,443521231499750041,4748434334677932361,36119410438503259561
%N A190875 E.g.f. exp(x+x^4).
%H A190875 Vincenzo Librandi, <a href="/A190875/b190875.txt">Table of n, a(n) for n = 0..105</a>
%F A190875 a(n) = n!*Sum_{j=0..n/3} binomial(n-3*j,j)/(n-3*j)!.
%F A190875 Recurrence: a(n) = a(n-1) + 4*(n-3)*(n-2)*(n-1)*a(n-4). - _Vaclav Kotesovec_, Jun 26 2013
%F A190875 a(n) ~ 2^(n/2-1)*exp(n^(1/4)/sqrt(2)-3*n/4)*n^(3*n/4). - _Vaclav Kotesovec_, Jun 26 2013
%t A190875 CoefficientList[Series[E^(x+x^4), {x, 0, 20}], x]* Range[0, 20]! (* _Vaclav Kotesovec_, Jun 26 2013 *)
%o A190875 (Maxima) a(n):=n!*sum(binomial(n-3*j,j)/(n-3*j)!,j,0,n/3);
%o A190875 (PARI) Vec(serlaplace(exp(x+x^4+O(x^66)))) /* _Joerg Arndt_, May 24 2011 */
%K A190875 nonn,changed
%O A190875 0,5
%A A190875 _Vladimir Kruchinin_, May 22 2011