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 A238250 #7 Jul 23 2025 10:49:01 %S A238250 121,804,6828,43456,284992,1473792,7616082,32986844,142361644, %T A238250 537301496,2020791427,6843417893,23099713493,71683038307,221767602558, %U A238250 640525984280,1844757869502,5018918602972,13619020527533,35234899933725 %N A238250 Number of (n+1)X(3+1) 0..1 arrays with 2X2 subblock sums lexicographically nondecreasing columnwise and rowwise. %C A238250 Column 3 of A238255 %H A238250 R. H. Hardin, <a href="/A238250/b238250.txt">Table of n, a(n) for n = 1..210</a> %H A238250 R. H. Hardin, <a href="/A238250/a238250.txt">Empirical recurrence of order 81</a> %F A238250 Empirical recurrence of order 81 (see link above) %e A238250 Some solutions for n=4 %e A238250 ..0..0..0..1....0..1..1..1....0..0..0..1....0..0..0..1....0..0..0..0 %e A238250 ..0..0..0..0....0..0..1..1....1..0..1..0....0..0..0..0....0..0..0..0 %e A238250 ..0..1..0..0....1..1..0..0....0..0..0..1....0..0..0..1....1..0..1..0 %e A238250 ..0..1..1..1....0..1..1..1....1..1..1..0....1..0..1..0....1..1..1..1 %e A238250 ..1..1..1..1....1..1..0..1....1..1..1..0....1..0..1..1....1..0..1..0 %K A238250 nonn %O A238250 1,1 %A A238250 _R. H. Hardin_, Feb 21 2014