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 A206465 #8 Jul 22 2025 19:27:32 %S A206465 25,1411,110889,68352739,61244865529,377599682448675, %T A206465 3848918441303655721,232902549300945882026755, %U A206465 26631802795003317433250214201,15822211869785299795988010016362883 %N A206465 Number of (n+1)X(n+1) 0..2 arrays with every 2X2 subblock having zero permanent. %C A206465 Diagonal of A206472 %H A206465 R. H. Hardin, <a href="/A206465/b206465.txt">Table of n, a(n) for n = 1..18</a> %e A206465 Some solutions for n=4 %e A206465 ..0..0..0..2..0....2..1..0..2..1....1..2..1..0..1....1..2..2..2..1 %e A206465 ..0..1..0..1..0....0..0..0..0..0....0..0..0..0..1....0..0..0..0..0 %e A206465 ..0..0..0..1..0....1..0..0..2..0....2..1..2..0..1....0..1..0..0..2 %e A206465 ..0..2..0..0..0....0..0..0..0..0....0..0..0..0..2....0..0..0..0..1 %e A206465 ..0..1..0..0..0....1..2..0..1..2....1..2..2..0..1....1..1..2..0..2 %K A206465 nonn %O A206465 1,1 %A A206465 _R. H. Hardin_ Feb 08 2012