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 A177473 #11 Oct 02 2024 07:54:51 %S A177473 1,1,2,6,18,61,272,1410,8048,51550,372995,2976679,25686748,239687103, %T A177473 2419267562,26194183096,301838412516,3692782460824,47891164866100, %U A177473 655887513203263,9449915113835659,142923476094740969,2265214890150056647,37539217881003574022,649054317768293760078 %N A177473 Number of permutations of order n avoiding the consecutive pattern 12'1'2. %C A177473 To avoid 12'1'2 means not to have four consecutive letters such that the first one is less than the fourth letter and the second letter is larger than the third one. %H A177473 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. %Y A177473 Cf. A117156, A177470, A177471, A177472, A177475, A177476, A177477, A177478, A177479, A177480, A177481, A177482, A177483, A177484, A376694. %K A177473 nonn %O A177473 0,3 %A A177473 Signy Olafsdottir (signy06(AT)ru.is), May 09 2010 %E A177473 Edited and terms a(0), a(10)-a(24) added by _Max Alekseyev_, Oct 01 2024