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 A227020 #7 Jul 23 2025 05:32:03 %S A227020 3,26,335,10050,786154,168973605,104606988712 %N A227020 Number of n X n (0,1,2) arrays of permanents of 2X2 subblocks of some (n+1)X(n+1) binary array with rows and columns of the latter in lexicographically nondecreasing order. %C A227020 Diagonal of A227025 %e A227020 Some solutions for n=4 %e A227020 ..0..0..1..1....0..1..0..1....0..0..1..1....0..0..0..1....0..1..0..1 %e A227020 ..0..1..0..0....0..0..0..1....0..1..0..0....0..0..2..0....0..0..0..0 %e A227020 ..1..0..0..1....0..1..1..1....1..0..1..1....0..1..0..1....1..1..0..1 %e A227020 ..0..0..1..2....1..1..0..1....0..0..1..1....0..0..0..0....1..1..1..2 %K A227020 nonn %O A227020 1,1 %A A227020 _R. H. Hardin_ Jun 27 2013