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 A251800 #6 Jun 02 2025 10:32:12 %S A251800 4206453,1271711747,413630526506,145329837643171,52256028323545001, %T A251800 19010586449609604592,6950854990205965398511, %U A251800 2548249927405969316226847,935397563567598908162444188,343605100623054019565873475859 %N A251800 Number of (n+1)X(7+1) 0..3 arrays with no 2X2 subblock having x11-x00 less than x10-x01. %C A251800 Column 7 of A251801 %H A251800 R. H. Hardin, <a href="/A251800/b251800.txt">Table of n, a(n) for n = 1..210</a> %e A251800 Some solutions for n=1 %e A251800 ..0..0..2..2..0..0..1..3....0..0..0..1..1..3..3..3....0..0..0..0..0..0..2..0 %e A251800 ..0..2..0..0..2..2..3..1....0..0..2..2..2..0..3..3....0..0..0..0..3..3..1..3 %K A251800 nonn %O A251800 1,1 %A A251800 _R. H. Hardin_, Dec 09 2014