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 A201535 #7 Jul 22 2025 16:17:22 %S A201535 6,69,633,7799,91425,983981,9526987,82847704,652848538,4712696751, %T A201535 31480011434,196280028176,1150650039753,6380377582098,33631853768986, %U A201535 169225758487160,815686475352515,3777731764480697,16854911299206527 %N A201535 Number of nX4 0..2 arrays with rows and columns lexicographically nondecreasing and every element equal to at least one horizontal or vertical neighbor. %C A201535 Column 4 of A201539 %H A201535 R. H. Hardin, <a href="/A201535/b201535.txt">Table of n, a(n) for n = 1..210</a> %F A201535 Empirical: a(n) is a polynomial of degree 80 for n>43 %e A201535 Some solutions for n=5 %e A201535 ..0..0..0..1....0..0..0..1....0..0..2..2....0..0..1..2....0..0..2..2 %e A201535 ..0..0..2..1....0..0..0..1....0..2..2..2....1..1..1..2....0..1..0..0 %e A201535 ..0..1..2..2....0..1..2..2....1..1..1..2....1..2..0..0....0..1..1..1 %e A201535 ..1..1..1..0....2..1..2..0....1..2..0..0....2..2..2..2....2..0..0..2 %e A201535 ..2..2..0..0....2..1..2..0....1..2..0..0....2..2..2..2....2..0..2..2 %K A201535 nonn %O A201535 1,1 %A A201535 _R. H. Hardin_ Dec 02 2011