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 A206951 #8 Jul 22 2025 19:49:44 %S A206951 3,81,11804,9803278,50967712088,1627105474024831, %T A206951 314368117565737962789,368862218847158027158758198 %N A206951 Number of n X n 0..2 arrays avoiding the pattern z z+1 z in any row, column or nw-to-se diagonal. %C A206951 Diagonal of A206957 %e A206951 Some solutions for n=4 %e A206951 ..1..1..1..0....2..1..0..2....2..0..0..1....2..0..1..1....2..0..0..0 %e A206951 ..1..2..2..2....1..2..2..1....1..1..0..1....2..1..0..1....0..1..1..0 %e A206951 ..0..2..2..2....1..0..1..2....2..2..1..0....1..2..2..2....0..1..1..2 %e A206951 ..2..0..0..1....0..0..2..0....2..2..2..0....1..0..0..0....2..2..1..1 %K A206951 nonn %O A206951 1,1 %A A206951 _R. H. Hardin_ Feb 13 2012