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 A207677 #8 Jul 22 2025 20:39:36 %S A207677 2,16,72,436,2310,11994,65564,379618,2306234,15546084,105736196, %T A207677 882008157,7460256028,79554888778,842718226878,10871887456045, %U A207677 151150820925264,2491064356652975,43353562677488606,900988265135221518 %N A207677 Number of n X n 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 1 1 1 vertically. %C A207677 Diagonal of A207682 %e A207677 Some solutions for n=4 %e A207677 ..0..1..1..0....1..1..0..0....0..1..1..0....0..1..0..0....1..0..0..1 %e A207677 ..0..1..0..0....0..0..1..0....1..0..0..1....0..0..1..0....1..1..1..0 %e A207677 ..0..0..1..0....0..1..1..0....1..1..1..1....0..1..0..0....0..1..1..1 %e A207677 ..0..1..1..0....0..1..0..0....0..0..1..0....0..0..1..0....1..0..0..1 %K A207677 nonn %O A207677 1,1 %A A207677 _R. H. Hardin_ Feb 19 2012