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 A209496 #8 Jul 22 2025 21:45:46 %S A209496 1,6,1938,9502354,416022303027,154401817037192112, %T A209496 485400266057664024464791 %N A209496 Number of n X n 0..4 arrays with every 2X2 subblock containing exactly one value repeat, and new values 0..4 introduced in row major order. %C A209496 Diagonal of A209503 %e A209496 Some solutions for n=4 %e A209496 ..0..0..1..0....0..1..0..0....0..0..0..1....0..1..0..2....0..0..0..0 %e A209496 ..2..1..2..0....0..2..1..2....1..2..3..0....2..2..0..3....1..2..3..2 %e A209496 ..1..3..1..2....2..1..0..0....2..3..1..3....0..1..2..0....2..3..0..3 %e A209496 ..3..4..4..4....3..1..2..3....1..1..2..1....0..3..1..0....4..2..2..0 %K A209496 nonn %O A209496 1,2 %A A209496 _R. H. Hardin_ Mar 09 2012