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 A221292 #5 Jul 23 2025 01:49:25 %S A221292 1,37,556,9107,172904,2890017,49684593,821323042,13475380990 %N A221292 Equals two maps: number of 4Xn binary arrays indicating the locations of corresponding elements equal to exactly two of their horizontal and antidiagonal neighbors in a random 0..3 4Xn array. %C A221292 Row 4 of A221290 %e A221292 Some solutions for n=3 %e A221292 ..0..1..0....0..0..0....0..0..1....0..1..0....0..1..1....0..1..0....0..0..1 %e A221292 ..0..0..0....0..1..0....0..1..0....0..1..0....1..1..0....1..0..0....1..0..0 %e A221292 ..1..1..0....0..1..1....1..1..1....1..0..0....0..0..0....0..0..1....0..1..1 %e A221292 ..0..0..0....1..1..0....0..0..0....0..1..0....1..1..0....0..0..0....1..0..0 %K A221292 nonn %O A221292 1,2 %A A221292 _R. H. Hardin_ Jan 09 2013