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 A207251 #7 Jul 22 2025 20:12:39 %S A207251 10,100,390,1950,9072,43498,206514,982940,4672690,22223478,105684192, %T A207251 502611290,2390250122,11367287780,54059152686,257088257194, %U A207251 1222630168560,5814441801566,27651641179470,131502438430740,625383900547134 %N A207251 Number of nX5 0..1 arrays avoiding 0 0 1 and 1 0 1 horizontally and 0 1 0 and 1 0 1 vertically. %C A207251 Column 5 of A207254 %H A207251 R. H. Hardin, <a href="/A207251/b207251.txt">Table of n, a(n) for n = 1..210</a> %F A207251 Empirical: a(n) = 3*a(n-1) +6*a(n-2) +a(n-3) +36*a(n-4) +49*a(n-5) +31*a(n-6) +66*a(n-7) +45*a(n-8) +15*a(n-9) -5*a(n-10) -16*a(n-11) -a(n-12) -a(n-13) +a(n-14) %e A207251 Some solutions for n=4 %e A207251 ..0..1..1..1..1....1..0..0..0..0....1..1..0..0..0....1..1..0..0..0 %e A207251 ..1..1..0..0..0....0..0..0..0..0....1..0..0..0..0....1..0..0..0..0 %e A207251 ..1..1..0..0..0....0..1..1..0..0....0..0..0..0..0....1..0..0..0..0 %e A207251 ..1..0..0..0..0....0..1..1..0..0....0..0..0..0..0....1..0..0..0..0 %K A207251 nonn %O A207251 1,1 %A A207251 _R. H. Hardin_ Feb 16 2012