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 A221336 #5 Jul 23 2025 01:50:58 %S A221336 4,68,790,10704,142792,1937900,26264018,356533300,4838763426, %T A221336 65677043240,891388869206 %N A221336 Number of nX4 arrays of occupancy after each element stays put or moves to some king-move neighbor, with every occupancy equal to zero or two. %C A221336 Column 4 of A221337 %e A221336 Some solutions for n=3 %e A221336 ..2..0..2..0....2..0..0..2....0..2..2..2....2..0..0..0....0..2..0..2 %e A221336 ..2..0..0..0....0..0..0..2....2..0..0..0....2..0..2..2....0..2..2..0 %e A221336 ..2..2..2..0....2..0..2..2....2..0..2..0....2..2..0..0....2..0..2..0 %K A221336 nonn %O A221336 1,1 %A A221336 _R. H. Hardin_ Jan 11 2013