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 A238251 #6 Jul 23 2025 10:49:08 %S A238251 286,2818,43456,523578,6683137,65450601,640472606,5080416791, %T A238251 40066932588,267891545518,1781590953402,10371478598345,60084341166190, %U A238251 311815187891138,1610762741432521,7583058204030841,35540971632237331 %N A238251 Number of (n+1)X(4+1) 0..1 arrays with 2X2 subblock sums lexicographically nondecreasing columnwise and rowwise. %C A238251 Column 4 of A238255 %H A238251 R. H. Hardin, <a href="/A238251/b238251.txt">Table of n, a(n) for n = 1..210</a> %e A238251 Some solutions for n=3 %e A238251 ..0..0..0..0..1....0..1..1..1..1....0..0..0..0..1....0..0..0..1..1 %e A238251 ..0..0..1..0..1....0..1..0..1..0....0..1..1..1..1....0..1..1..1..1 %e A238251 ..0..1..0..1..0....1..1..0..1..1....0..0..1..0..0....1..1..1..1..1 %e A238251 ..1..1..1..1..1....1..0..1..1..1....1..1..0..1..1....1..1..1..0..0 %K A238251 nonn %O A238251 1,1 %A A238251 _R. H. Hardin_, Feb 21 2014