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 A251225 #6 Jul 23 2025 13:11:41 %S A251225 2084,72985,2515011,87024544,3007738372,103986727042,3594807908974, %T A251225 124275144041759,4296252165879236,148523812761431640, %U A251225 5134547519926425245,177504075991625903000,6136411350172751480986,212139042310887309043390 %N A251225 Number of (n+1)X(5+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 A251225 Column 5 of A251228 %H A251225 R. H. Hardin, <a href="/A251225/b251225.txt">Table of n, a(n) for n = 1..210</a> %F A251225 Empirical: a(n) = 21*a(n-1) +554*a(n-2) -1341*a(n-3) -56723*a(n-4) -7614*a(n-5) +2277951*a(n-6) +445571*a(n-7) -46434220*a(n-8) +32482888*a(n-9) +467723527*a(n-10) -889155765*a(n-11) -1188153000*a(n-12) +4147652079*a(n-13) -132672964*a(n-14) -8042725671*a(n-15) +4499239992*a(n-16) +7457116236*a(n-17) -6933658033*a(n-18) -3126154333*a(n-19) +4558838720*a(n-20) +384337441*a(n-21) -1441277326*a(n-22) +61108155*a(n-23) +221926922*a(n-24) -13300621*a(n-25) -18641195*a(n-26) -491525*a(n-27) +335825*a(n-28) +5625*a(n-29) %e A251225 Some solutions for n=2 %e A251225 ..1..1..0..0..1..0....1..0..1..0..0..0....0..1..1..0..1..0....0..1..1..0..0..1 %e A251225 ..1..0..0..1..1..0....0..0..1..1..0..0....0..0..0..0..1..1....0..0..1..1..1..0 %e A251225 ..1..0..0..0..0..0....1..1..0..1..0..0....0..0..1..0..0..1....1..1..0..0..1..0 %K A251225 nonn %O A251225 1,1 %A A251225 _R. H. Hardin_, Nov 30 2014