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 A309331 #10 Mar 25 2024 09:53:59 %S A309331 0,1,1,2,5,9,16,32,61,114,219,418,792,1510,2878,5473,10421,19847, %T A309331 37776,71917,136931,260680,496278,944847,1798804,3424569,6519790, %U A309331 12412480,23631034,44989208,85651217,163064109,310444213,591028898,1125210433 %N A309331 Expansion of (x+x^3+x^5)/(1-x-3*x^3-x^5). %C A309331 a(n) is the number of 231-avoiding permutations of length n that have order 1 or 3. %H A309331 Amanda Burcroff and Colin Defant, <a href="https://arxiv.org/abs/1907.09451">Pattern-Avoiding Permutation Powers</a>, arXiv:1907.09451 [math.CO], 2019. %H A309331 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,0,3,0,1). %F A309331 G.f.: (1-x+x^2)*(1+x+x^2)/(1-x-3*x^3-x^5). %K A309331 easy,nonn %O A309331 0,4 %A A309331 _Colin Defant_, Jul 23 2019