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 A267227 #10 Feb 06 2018 11:26:16 %S A267227 4,16,54,176,564,1790,5646,17732,55512,173354,540258,1680848,5221740, %T A267227 16200758,50204790,155413724,480622848,1484980802,4584213642, %U A267227 14140323560,43583756436,134239102286,413179757214,1270924525556,3906925144104 %N A267227 Number of length-n 0..3 arrays with no following elements greater than or equal to the first repeated value. %C A267227 Column 3 of A267232. %H A267227 R. H. Hardin, <a href="/A267227/b267227.txt">Table of n, a(n) for n = 1..210</a> %F A267227 Empirical: a(n) = 9*a(n-1) - 29*a(n-2) + 39*a(n-3) - 18*a(n-4) for n > 5. %F A267227 Conjectures from _Colin Barker_, Feb 05 2018: (Start) %F A267227 G.f.: 2*x*(2 - 10*x + 13*x^2 - x^3 - 3*x^4) / ((1 - x)*(1 - 2*x)*(1 - 3*x)^2). %F A267227 a(n) = (-9 - 9*2^n + 11*3^(1+n) + 2*3^n*n) / 18 for n>1. %F A267227 (End) %e A267227 Some solutions for n=6: %e A267227 2 0 1 2 3 2 1 2 3 0 3 1 1 3 2 3 %e A267227 3 1 3 0 0 1 2 3 1 1 2 0 0 3 0 2 %e A267227 2 0 1 2 3 3 3 0 3 0 1 2 3 0 2 3 %e A267227 0 3 3 3 1 2 0 2 1 1 3 1 0 2 3 0 %e A267227 3 3 2 3 1 2 1 3 2 2 2 0 1 1 1 1 %e A267227 0 2 0 0 0 0 2 1 2 3 0 3 3 0 1 2 %Y A267227 Cf. A267232. %K A267227 nonn %O A267227 1,1 %A A267227 _R. H. Hardin_, Jan 12 2016