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 A234115 #7 Jun 02 2025 09:11:48 %S A234115 31,1361,231713,157630963,427196005695,4625943683805313, %T A234115 200376051988817866625,34754816964141969688314115, %U A234115 24157262935852623408023272643359,67332158893994957162261589597358347857 %N A234115 Number of (n+1)X(n+1) 0..2 arrays with every 2X2 subblock having the absolute values of all six edge and diagonal differences no larger than 1. %C A234115 Diagonal of A234122 %H A234115 R. H. Hardin, <a href="/A234115/b234115.txt">Table of n, a(n) for n = 1..13</a> %e A234115 Some solutions for n=2 %e A234115 ..2..1..2....2..1..1....1..2..1....1..1..1....2..1..2....1..1..1....1..0..1 %e A234115 ..2..1..2....1..2..1....2..1..2....0..1..0....1..2..2....1..0..1....0..0..1 %e A234115 ..2..2..1....1..2..1....2..1..2....0..0..0....2..2..1....0..0..1....1..0..1 %K A234115 nonn %O A234115 1,1 %A A234115 _R. H. Hardin_, Dec 19 2013