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 A204031 #7 Jul 22 2025 17:42:54 %S A204031 16,164,2928,44366,969528,16895850,397550036,7576693894,184631622106, %T A204031 3777035543236,93707916130348,2028328695512904,50826307266520194 %N A204031 Number of (n+1)X(n+1) 0..1 arrays with the sums of 2X2 subblocks nondecreasing rightwards and downwards. %C A204031 Diagonal of A204039 %e A204031 Some solutions for n=4 %e A204031 ..0..1..1..1..0....1..1..0..0..0....1..0..1..1..0....0..0..1..1..1 %e A204031 ..1..0..0..0..1....0..0..1..1..1....0..1..0..1..1....0..1..0..1..1 %e A204031 ..0..1..1..1..0....1..1..0..1..0....1..1..1..1..1....0..1..1..1..1 %e A204031 ..0..1..0..1..1....0..1..1..1..1....1..1..1..1..1....0..1..1..1..1 %e A204031 ..0..1..1..1..0....1..1..1..1..1....1..1..1..1..1....0..1..1..1..1 %K A204031 nonn %O A204031 1,1 %A A204031 _R. H. Hardin_ Jan 09 2012