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 A177470 #18 Oct 02 2024 04:16:06 %S A177470 1,1,2,6,18,70,300,1435,7910,47376,316008,2314158,18331236,158024724, %T A177470 1462752720,14497475850,153488070450,1724035906450,20515906356660, %U A177470 257720354712106,3406481187714176,47293781230517640,687760952277462336,10456003715906638162,165890170459303164420 %N A177470 Number of permutations of order n avoiding the consecutive pattern 11'22'. %C A177470 To avoid 11'22' means not to have four consecutive letters such that the first letter is less than the third one and the second letter is less than the fourth one. %H A177470 S. Kitaev, <a href="https://doi.org/10.1016/j.dam.2006.09.011">Introduction to partially ordered patterns</a>, Discrete Applied Mathematics 155 (2007), 929-944. %H A177470 Rémy Sigrist, <a href="/A177470/a177470.txt">C program</a> %o A177470 (C) // See Links section. %Y A177470 Cf. A117156, A177471, A177472, A177473, A177475, A177476, A177477, A177478, A177479, A177480, A177481, A177482, A177483, A177484, A376694. %K A177470 nonn %O A177470 0,3 %A A177470 Signy Olafsdottir (signy06(AT)ru.is), May 09 2010 %E A177470 a(0) = 1 and a(10)-a(16) from _Rémy Sigrist_, Mar 13 2023 %E A177470 Edited and a(17)-a(24) added by _Max Alekseyev_, Oct 01 2024