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 A381858 #26 May 13 2025 09:53:28
%S A381858 1,1,2,5,12,26,56,125,279,618,1367,3030,6720,14896,33013,73173,162198,
%T A381858 359525,796900,1766366,3915256,8678393,19236131,42637934,94509351,
%U A381858 209485238,464335636,1029225640,2281335673,5056707001,11208471338,24844197877,55068541516
%N A381858 a(n) is the number of permutations of [n] that avoid 312 and 4321 and whose square avoids 231.
%H A381858 Michael De Vlieger, <a href="/A381858/b381858.txt">Table of n, a(n) for n = 0..2893</a>
%H A381858 Kassie Archer and Noel Bourne, <a href="https://arxiv.org/abs/2505.05218">Pattern avoidance in compositions and powers of permutations</a>, arXiv:2505.05218 [math.CO], 2025. See p. 8.
%H A381858 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,1,2,3,2).
%F A381858 G.f.: 1/(1-x-x^2-2*x^3-3*x^4-2*x^5).
%t A381858 LinearRecurrence[{1,1,2,3,2},{1, 1, 2, 5, 12},33] (* _James C. McMahon_, Mar 10 2025 *)
%K A381858 nonn,easy
%O A381858 0,3
%A A381858 _Kassie Archer_, Mar 10 2025