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 A220330 #6 Jul 23 2025 01:04:03 %S A220330 1,12,92,572,4062,29467,213225,1540686,11163495,80656708,581473349, %T A220330 4190483128,30199355040,217538559602,1566825952174,11283025994195, %U A220330 81236036737903,584831754731217,4210022381269251,30304818855812080 %N A220330 Equals two maps: number of 3Xn binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and antidiagonal neighbors in a random 0..1 3Xn array. %C A220330 Row 3 of A220328 %H A220330 R. H. Hardin, <a href="/A220330/b220330.txt">Table of n, a(n) for n = 1..22</a> %e A220330 Some solutions for n=3 %e A220330 ..0..1..0....0..0..0....0..0..0....0..1..1....0..1..0....0..1..0....0..0..0 %e A220330 ..0..1..0....1..0..1....1..1..0....0..1..0....0..1..1....1..1..0....0..0..1 %e A220330 ..0..0..0....1..1..0....0..1..0....1..1..0....0..0..0....0..1..0....0..1..0 %K A220330 nonn %O A220330 1,2 %A A220330 _R. H. Hardin_ Dec 10 2012