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 A268751 #10 Mar 03 2016 21:34:16 %S A268751 0,0,1,374,16140983,173996758190594,791857392420720220446647, %T A268751 2285085934263252199073238394141449534, %U A268751 5841526335200139692050292842849347521755651331941759,17585875137049122003330684747231440185032966840579881629527695901745706 %N A268751 Number of sequences with n copies each of 1,2,...,n avoiding the pattern 12...n. %H A268751 Alois P. Heinz, <a href="/A268751/b268751.txt">Table of n, a(n) for n = 0..27</a> %F A268751 a(n) = A034841(n) - A268485(n). %e A268751 a(2) = 1: 2211. %e A268751 a(3) = 374: 111333222, 113133222, 113313222, ..., 333221121, 333221211, 333222111. %Y A268751 Main diagonal of A269129. %Y A268751 Cf. A034841, A268485. %K A268751 nonn %O A268751 0,4 %A A268751 _Alois P. Heinz_, Feb 12 2016