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 A216331 #7 Jul 22 2025 23:30:32 %S A216331 1,2,15,726,2387180,37060650272,148049849072167133, %T A216331 2765650089185458968363718 %N A216331 Number of horizontal and antidiagonal neighbor colorings of the even squares of an n X n array with new integer colors introduced in row major order. %C A216331 Diagonal of A216338 %e A216331 Some solutions for n=4 %e A216331 ..0..x..1..x....0..x..1..x....0..x..1..x....0..x..1..x....0..x..1..x %e A216331 ..x..0..x..1....x..0..x..2....x..2..x..0....x..2..x..3....x..0..x..2 %e A216331 ..2..x..3..x....2..x..0..x....1..x..2..x....3..x..2..x....3..x..4..x %e A216331 ..x..2..x..1....x..3..x..4....x..0..x..3....x..1..x..3....x..2..x..5 %K A216331 nonn %O A216331 1,2 %A A216331 _R. H. Hardin_ Sep 04 2012