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 A284216 #10 Aug 22 2025 13:27:13 %S A284216 2,6,19,62,212,751,2719,10002,37258,140108,530646,2021127,7733421, %T A284216 29702087,114438213,442099674,1711885120,6642102554,25817134600, %U A284216 100506778916,391827603432,1529486575678,5977159139018,23382840951503,91561688560429,358847611430293,1407524281467975 %N A284216 Number of n X 2 0..1 arrays with the number of 1's horizontally or antidiagonally adjacent to some 0 equal to the number of 0's adjacent to some 1, with top left element zero. %H A284216 R. H. Hardin, <a href="/A284216/b284216.txt">Table of n, a(n) for n = 1..210</a> %e A284216 Some solutions for n=4: %e A284216 ..0..1. .0..0. .0..1. .0..0. .0..1. .0..0. .0..0. .0..1. .0..0. .0..1 %e A284216 ..0..1. .0..0. .1..1. .0..0. .1..0. .1..1. .1..1. .0..1. .1..1. .1..1 %e A284216 ..1..1. .0..1. .0..0. .0..0. .1..0. .1..0. .0..0. .0..1. .1..1. .1..0 %e A284216 ..1..0. .1..0. .1..1. .0..1. .0..1. .0..1. .1..1. .0..1. .1..1. .0..1 %Y A284216 Column 2 of A284222. %K A284216 nonn %O A284216 1,1 %A A284216 _R. H. Hardin_, Mar 23 2017