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 A206865 #8 Jul 22 2025 19:44:30 %S A206865 2,16,211,7675,728935,159327093,90497940567,125050630010443, %T A206865 420541855354109634,3548467633453651525361,73505549006944543732634211, %U A206865 3751209136697289848938709033475 %N A206865 Number of n X n 0..1 arrays avoiding 0 0 0 horizontally and 1 0 1 vertically. %C A206865 Diagonal of A206871 %e A206865 Some solutions for n=4 %e A206865 ..1..0..0..1....0..1..1..0....1..1..0..0....0..0..1..0....0..1..0..0 %e A206865 ..1..1..0..0....1..1..0..0....0..1..1..1....0..0..1..0....1..0..1..1 %e A206865 ..1..0..1..0....0..1..0..0....0..1..0..1....1..1..0..0....1..0..0..1 %e A206865 ..1..0..0..1....0..1..1..0....1..1..0..1....1..1..0..0....1..0..0..1 %K A206865 nonn %O A206865 1,1 %A A206865 _R. H. Hardin_ Feb 13 2012