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 A231657 #6 Jul 23 2025 06:36:42 %S A231657 3,15,93,458,2163,10789,53813,265397,1311447,6493700,32130833, %T A231657 158937397,786355013,3890673454,19249161646,95235762295,471186213619, %U A231657 2331226488364,11533889645847,57064690337149,282331462742945,1396854097460108 %N A231657 Number of nX2 0..2 arrays with no element less than a strict majority of its horizontal, vertical and antidiagonal neighbors. %C A231657 Column 2 of A231663 %H A231657 R. H. Hardin, <a href="/A231657/b231657.txt">Table of n, a(n) for n = 1..210</a> %F A231657 Empirical: a(n) = 9*a(n-1) -28*a(n-2) +65*a(n-3) -167*a(n-4) +235*a(n-5) -237*a(n-6) +327*a(n-7) -345*a(n-8) +267*a(n-9) -198*a(n-10) +193*a(n-11) -88*a(n-12) +52*a(n-13) -20*a(n-14) +16*a(n-15) %e A231657 Some solutions for n=7 %e A231657 ..2..0....1..0....0..0....0..2....0..0....1..1....0..0....0..0....0..0....2..2 %e A231657 ..0..0....0..0....2..0....0..0....1..0....1..2....0..2....0..0....1..0....2..0 %e A231657 ..2..1....0..2....1..0....0..1....2..0....1..2....1..1....0..1....0..1....0..0 %e A231657 ..1..1....0..1....0..0....2..2....0..1....1..1....1..1....1..0....0..0....2..0 %e A231657 ..2..1....0..0....2..2....2..0....0..0....2..1....2..1....0..0....0..2....0..0 %e A231657 ..0..0....0..1....2..0....0..0....0..0....2..1....1..0....0..1....2..1....2..1 %e A231657 ..0..0....0..0....0..0....2..0....2..2....2..1....0..0....1..2....1..1....2..1 %K A231657 nonn %O A231657 1,1 %A A231657 _R. H. Hardin_, Nov 12 2013