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 A215920 #7 Jul 22 2025 23:27:35 %S A215920 1,1,4,602,322768,33093356640,12954733199158688, %T A215920 2562708954818067388122544 %N A215920 Number of diagonal and antidiagonal neighbor colorings of the odd squares of an n X n array with new integer colors introduced in row major order. %C A215920 Diagonal of A215924 %e A215920 Some solutions for n=4 %e A215920 ..x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..1....x..0..x..0 %e A215920 ..1..x..2..x....1..x..2..x....2..x..3..x....1..x..2..x....1..x..2..x %e A215920 ..x..0..x..0....x..3..x..1....x..0..x..0....x..0..x..1....x..0..x..0 %e A215920 ..3..x..2..x....4..x..4..x....4..x..1..x....3..x..4..x....3..x..1..x %K A215920 nonn %O A215920 1,3 %A A215920 _R. H. Hardin_ Aug 27 2012