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 A303676 #6 Sep 16 2020 19:06:58 %S A303676 1,5,9,28,76,177,367,774,1684,3639,7597,15617,32101,66074,135096, %T A303676 274104,553668,1116275,2245277,4501938,9000074,17953486,35749382, %U A303676 71056212,140977366,279246077,552333115,1091040731 %N A303676 Number of n X n 0..1 arrays with every element unequal to 0, 1 or 3 king-move adjacent elements, with upper left element zero. %C A303676 Diagonal of A303682. %e A303676 Some solutions for n=5 %e A303676 ..0..0..1..1..0. .0..1..1..0..0. .0..0..0..0..1. .0..0..0..1..1 %e A303676 ..0..1..1..1..1. .1..1..1..1..0. .0..0..0..0..0. .0..0..0..0..1 %e A303676 ..1..1..1..1..1. .1..1..1..1..1. .0..0..0..0..0. .0..0..0..0..0 %e A303676 ..1..1..1..1..1. .1..1..1..1..1. .0..0..0..0..0. .0..0..0..0..0 %e A303676 ..1..1..1..1..0. .0..1..1..1..1. .1..0..0..0..0. .0..0..0..0..0 %Y A303676 Cf. A303682. %K A303676 nonn %O A303676 1,2 %A A303676 _R. H. Hardin_, Apr 28 2018