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 A251223 #6 Jul 23 2025 13:11:28 %S A251223 171,1892,20782,228689,2515011,27662994,304255924,3346446223, %T A251223 36806732398,404828461391,4452610577279,48973192395914, %U A251223 538644351143299,5924419545393448,65161264266944558,716693058210959682 %N A251223 Number of (n+1)X(3+1) 0..1 arrays with no 2X2 subblock having the minimum of its diagonal elements greater than the absolute difference of its antidiagonal elements. %C A251223 Column 3 of A251228 %H A251223 R. H. Hardin, <a href="/A251223/b251223.txt">Table of n, a(n) for n = 1..210</a> %F A251223 Empirical: a(n) = 8*a(n-1) +39*a(n-2) -48*a(n-3) -210*a(n-4) +88*a(n-5) +260*a(n-6) -199*a(n-7) +36*a(n-8) %e A251223 Some solutions for n=3 %e A251223 ..0..1..0..0....0..1..0..1....0..0..1..0....1..1..0..0....0..0..0..1 %e A251223 ..1..1..1..1....0..1..0..1....0..1..0..0....0..0..0..1....1..1..0..0 %e A251223 ..0..0..0..0....1..1..0..0....0..1..1..0....0..0..0..1....0..1..0..0 %e A251223 ..1..1..1..1....0..1..1..1....1..1..0..0....0..1..0..0....1..0..0..0 %K A251223 nonn %O A251223 1,1 %A A251223 _R. H. Hardin_, Nov 30 2014