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 A251264 #6 Jun 02 2025 10:19:44 %S A251264 120,772,4930,32636,217634,1457326,9772880,65582500,440223510, %T A251264 2955392154,19841767762,133216123406,894412534702,6005113336592, %U A251264 40318603143004,270701212074848,1817502901804920,12202817537105258,81930416102796122 %N A251264 Number of (n+1)X(4+1) 0..1 arrays with no 2X2 subblock having x11-x00 less than x10-x01. %C A251264 Column 4 of A251268 %H A251264 R. H. Hardin, <a href="/A251264/b251264.txt">Table of n, a(n) for n = 1..210</a> %F A251264 Empirical: a(n) = 10*a(n-1) -11*a(n-2) -119*a(n-3) +288*a(n-4) +236*a(n-5) -1082*a(n-6) +141*a(n-7) +1550*a(n-8) -732*a(n-9) -936*a(n-10) +648*a(n-11) +181*a(n-12) -198*a(n-13) +14*a(n-14) +13*a(n-15) -2*a(n-16) %e A251264 Some solutions for n=4 %e A251264 ..0..0..0..0..0....0..0..1..0..0....0..0..0..0..1....0..1..1..0..1 %e A251264 ..0..0..0..0..1....0..0..0..1..1....1..1..1..1..1....0..0..0..1..1 %e A251264 ..0..0..1..1..0....0..0..1..0..1....0..0..0..0..0....0..0..0..1..1 %e A251264 ..0..0..0..0..1....1..1..0..1..1....0..0..0..0..0....0..0..0..1..1 %e A251264 ..0..0..0..1..0....0..0..1..0..0....0..0..0..0..1....0..0..1..0..0 %K A251264 nonn %O A251264 1,1 %A A251264 _R. H. Hardin_, Dec 01 2014