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 A260833 #6 Jun 02 2025 12:11:15 %S A260833 48,131,700,2235,3828,19718,80516,181176,766388,3885356,12122540, %T A260833 43330160,229463444,972300920,3559612500,17890822312,91527500980 %N A260833 Number of (n+2)X(n+2) 0..1 arrays with each 3X3 subblock having clockwise perimeter pattern 00000001 00000011 or 00010101. %C A260833 Diagonal of A260841 %e A260833 Some solutions for n=4 %e A260833 ..0..0..0..0..0..0....0..1..0..0..0..1....0..0..0..0..1..1....0..0..0..0..0..0 %e A260833 ..1..0..0..1..1..0....0..1..0..0..1..1....1..1..0..0..1..0....0..0..0..0..1..0 %e A260833 ..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....1..1..0..0..1..0 %e A260833 ..0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0....0..0..0..0..0..0 %e A260833 ..1..1..0..0..1..0....0..1..0..0..1..0....0..1..0..0..1..0....0..0..0..0..0..0 %e A260833 ..0..0..0..0..1..0....0..1..0..0..0..1....1..1..0..0..1..1....1..0..0..1..1..0 %Y A260833 Cf. A260841 %K A260833 nonn %O A260833 1,1 %A A260833 _R. H. Hardin_, Aug 01 2015