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 A201534 #7 Jul 22 2025 16:17:16 %S A201534 3,25,111,633,3354,16393,72811,293831,1087857,3735546,12012530, %T A201534 36466979,105202136,289996482,767360174,1956720113,4824093641, %U A201534 11531663892,26793101230,60636948110,133921364986,289121431541,611037886807 %N A201534 Number of nX3 0..2 arrays with rows and columns lexicographically nondecreasing and every element equal to at least one horizontal or vertical neighbor. %C A201534 Column 3 of A201539 %H A201534 R. H. Hardin, <a href="/A201534/b201534.txt">Table of n, a(n) for n = 1..210</a> %F A201534 Empirical: a(n) is a polynomial of degree 26 for n>13 %e A201534 Some solutions for n=7 %e A201534 ..0..0..2....0..0..1....0..0..0....0..0..2....0..0..0....0..0..0....1..1..1 %e A201534 ..0..2..2....0..2..1....0..0..0....0..1..2....0..2..2....0..0..2....1..1..2 %e A201534 ..1..1..0....0..2..1....0..2..2....0..1..2....1..1..2....1..1..2....1..2..2 %e A201534 ..2..1..0....2..0..0....1..1..1....0..1..2....1..1..2....1..2..1....1..2..2 %e A201534 ..2..2..1....2..0..0....1..1..1....0..2..2....2..1..1....1..2..1....2..1..1 %e A201534 ..2..2..1....2..0..2....2..0..0....2..2..1....2..1..1....2..2..1....2..2..1 %e A201534 ..2..2..1....2..2..2....2..0..0....2..2..1....2..2..1....2..2..1....2..2..1 %K A201534 nonn %O A201534 1,1 %A A201534 _R. H. Hardin_ Dec 02 2011