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 A195976 #7 Jun 02 2025 04:16:41 %S A195976 16,78,134,256,519,1280,2718,5830,12799,28969,64536,144480,323887, %T A195976 730358,1647281,3720888,8406355,19026721,43091379,97668401,221445855, %U A195976 502417344,1140305840,2589100946,5880051614,13357939515,30351874554,68979138844 %N A195976 Number of nX6 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 2,0,1,3,4 for x=0,1,2,3,4. %C A195976 Every 0 is next to 0 2's, every 1 is next to 1 0's, every 2 is next to 2 1's, every 3 is next to 3 3's, every 4 is next to 4 4's %C A195976 Column 6 of A195978 %H A195976 R. H. Hardin, <a href="/A195976/b195976.txt">Table of n, a(n) for n = 1..200</a> %e A195976 Some solutions for n=4 %e A195976 ..1..2..2..1..1..2....0..1..1..0..0..1....1..0..1..2..1..0....0..1..2..1..0..0 %e A195976 ..0..1..1..0..0..1....0..1..1..0..0..1....1..1..2..2..1..1....0..1..2..1..0..0 %e A195976 ..0..1..1..1..1..1....1..1..1..0..0..1....0..1..2..1..0..1....0..1..2..1..0..0 %e A195976 ..1..1..0..1..1..0....1..0..1..1..1..2....0..1..2..1..0..1....0..1..2..1..0..0 %K A195976 nonn %O A195976 1,1 %A A195976 _R. H. Hardin_ Sep 25 2011