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 A183323 #8 Jul 22 2025 08:49:31 %S A183323 1,2,6,27,289,4740,128371,6115158,505971397,73890230419, %T A183323 19136191954838,8704355999401819,6908686513461201175, %U A183323 9552034660752931158279 %N A183323 Number of n X n binary arrays with each 1 adjacent to exactly two other 1s. %C A183323 Diagonal of A183328 %e A183323 Some solutions for 6X6 %e A183323 ..1..1..1..0..0..0....0..1..1..1..1..0....0..0..0..1..1..1....0..0..1..1..1..1 %e A183323 ..1..0..1..0..1..1....0..1..0..0..1..1....0..0..1..1..0..1....0..0..1..0..0..1 %e A183323 ..1..0..1..0..1..1....1..1..0..0..0..1....0..1..1..0..1..1....1..1..1..0..0..1 %e A183323 ..1..1..1..0..0..0....1..0..0..0..1..1....0..1..0..1..1..0....1..0..0..0..0..1 %e A183323 ..0..0..0..1..1..0....1..1..0..1..1..0....0..1..0..1..0..0....1..0..0..0..1..1 %e A183323 ..0..0..0..1..1..0....0..1..1..1..0..0....0..1..1..1..0..0....1..1..1..1..1..0 %K A183323 nonn %O A183323 1,2 %A A183323 _R. H. Hardin_ Jan 03 2011