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 A189690 #7 Jul 22 2025 11:52:38 %S A189690 8,64,292,1298,5172,20316,77752,295720,1117080,4209924,15835990, %T A189690 59521532,223600028,839772726,3153450118,11840705184,44458053838, %U A189690 166922053694,626717259422,2353026409758,8834468527674,33169066709822,124533341936372 %N A189690 Number of nX3 binary arrays without the pattern 0 0 1 diagonally, vertically or antidiagonally. %C A189690 Column 3 of A189696 %H A189690 R. H. Hardin, <a href="/A189690/b189690.txt">Table of n, a(n) for n = 1..200</a> %F A189690 Empirical: a(n) = 7*a(n-1) -9*a(n-2) -31*a(n-3) +76*a(n-4) +22*a(n-5) -173*a(n-6) +69*a(n-7) +151*a(n-8) -111*a(n-9) -48*a(n-10) +52*a(n-11) +4*a(n-12) -8*a(n-13) %e A189690 Some solutions for 4X3 %e A189690 ..1..1..0....0..0..0....0..1..0....0..0..1....0..1..1....1..1..0....1..1..0 %e A189690 ..1..1..1....1..1..1....1..1..1....1..1..0....1..0..0....0..0..0....1..1..1 %e A189690 ..0..1..0....1..1..1....1..1..1....1..1..1....1..1..0....0..0..0....1..0..0 %e A189690 ..0..1..0....0..1..0....0..1..1....0..1..0....0..0..0....0..0..0....0..0..1 %K A189690 nonn %O A189690 1,1 %A A189690 _R. H. Hardin_ Apr 25 2011