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 A301901 #6 Aug 20 2020 11:48:12 %S A301901 1,1,3,5,12,532,8781,952467,81388360,24626668920,14235727386501, %T A301901 14622615341736656,38187293105036003115,169994743921070851334774, %U A301901 1720618701132822565695718755 %N A301901 Number of n X n 0..1 arrays with every element equal to 0, 2 or 3 horizontally or antidiagonally adjacent elements, with upper left element zero. %C A301901 Diagonal of A301906. %e A301901 Some solutions for n=5 %e A301901 ..0..1..1..0..1. .0..1..1..0..0. .0..1..1..0..0. .0..1..0..1..0 %e A301901 ..1..1..1..0..0. .1..1..0..0..1. .1..1..0..0..1. .0..1..0..1..0 %e A301901 ..0..1..0..0..0. .0..1..0..0..1. .1..1..1..0..1. .0..1..0..1..0 %e A301901 ..1..1..1..0..0. .0..1..0..0..0. .0..1..1..0..0. .0..1..0..1..0 %e A301901 ..1..1..0..0..1. .0..1..0..0..1. .1..1..0..0..1. .0..1..0..1..0 %Y A301901 Cf. A301906. %K A301901 nonn %O A301901 1,3 %A A301901 _R. H. Hardin_, Mar 28 2018