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 A099931 #18 May 07 2025 09:40:34
%S A099931 1,29,1015,34307,1166438,39618670,1345902818,45720876202,
%T A099931 1553165059215,52761884311059,1792350941301921,60887169888069525,
%U A099931 2068371426604585180,70263741326790571820,2386898833730186862100,81084296605231967961956,2754479185745716380504749
%N A099931 a(n) = Pell(n) * Pell(n-1) * Pell(n-2) * Pell(n-3) / 120.
%H A099931 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (29,174,-174,-29,1).
%F A099931 G.f.: x^4 / ((1-x)*(1+6x+x^2)*(1-34x+x^2)).
%F A099931 a(n) = 29*a(n-1) + 174*a(n-2) - 174*a(n-3) - 29*a(n-4) + a(n-5). - _Klaus Purath_, Oct 17 2020
%F A099931 G.f.: x^4 * exp( Sum_{k>=1} Pell(5*k)/Pell(k) * x^k/k ). - _Seiichi Manyama_, May 07 2025
%Y A099931 Cf. A000129. Fourth column of triangle A099927.
%K A099931 nonn,easy
%O A099931 4,2
%A A099931 _Ralf Stephan_, Nov 03 2004