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 A284335 #6 Apr 05 2020 22:54:52 %S A284335 2,4,13,34,118,419,1481,5394,19848,73880,277222,1047495,3977615, %T A284335 15169751,58074521,223081286,859450114,3319751314,12852496680, %U A284335 49860496892,193783946748,754379484650,2941051327294,11481400024511,44875877924939 %N A284335 Number of 2 X n 0..1 arrays with the number of 1's horizontally, diagonally or antidiagonally adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero. %C A284335 Row 2 of A284334. %H A284335 R. H. Hardin, <a href="/A284335/b284335.txt">Table of n, a(n) for n = 1..210</a> %e A284335 Some solutions for n=4 %e A284335 ..0..1..1..0. .0..1..1..0. .0..0..0..0. .0..0..1..0. .0..0..1..1 %e A284335 ..0..1..0..1. .0..1..1..0. .1..1..1..1. .1..1..1..0. .0..1..0..1 %Y A284335 Cf. A284334. %K A284335 nonn %O A284335 1,1 %A A284335 _R. H. Hardin_, Mar 25 2017