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 A207544 #10 Jul 22 2025 20:33:45 %S A207544 3,81,14974,18584111,151596413811,8153351029428092, %T A207544 2876868686935789680075,6662940552094334528016043729, %U A207544 101291421007307048419298014635301970 %N A207544 Number of n X n 0..2 arrays avoiding the pattern z-2 z-1 z in any row, column, nw-to-se diagonal or ne-to-sw antidiagonal. %C A207544 Diagonal of A207550 %e A207544 Some solutions for n=4 %e A207544 ..0..2..0..2....2..0..0..1....0..2..2..0....0..2..2..2....2..2..1..2 %e A207544 ..2..2..0..2....1..1..0..1....1..0..0..0....1..1..0..2....2..1..0..0 %e A207544 ..2..0..1..0....0..0..1..0....0..2..1..2....0..0..1..0....1..1..1..0 %e A207544 ..0..2..1..0....1..1..0..0....0..0..0..0....1..2..0..2....0..1..0..2 %K A207544 nonn %O A207544 1,1 %A A207544 _R. H. Hardin_ Feb 18 2012