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 A207119 #7 Jul 22 2025 20:02:42 %S A207119 9,81,288,1024,2560,6400,13200,27225,49665,90601,151704,254016,399168, %T A207119 627264,938520,1404225,2020425,2907025,4051080,5645376,7660224, %U A207119 10394176,13789048,18292729,23801505,30969225,39622800,50694400,63909120,80568576 %N A207119 Number of nX4 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 0 1 and 0 1 1 vertically. %C A207119 Column 4 of A207123 %H A207119 R. H. Hardin, <a href="/A207119/b207119.txt">Table of n, a(n) for n = 1..210</a> %F A207119 Empirical: a(n) = 2*a(n-1) +6*a(n-2) -14*a(n-3) -14*a(n-4) +42*a(n-5) +14*a(n-6) -70*a(n-7) +70*a(n-9) -14*a(n-10) -42*a(n-11) +14*a(n-12) +14*a(n-13) -6*a(n-14) -2*a(n-15) +a(n-16) %e A207119 Some solutions for n=4 %e A207119 ..1..1..1..1....1..1..1..1....1..0..1..1....0..1..1..0....0..1..1..0 %e A207119 ..1..0..0..0....1..1..1..1....1..1..0..1....1..1..0..0....1..0..1..1 %e A207119 ..0..1..1..1....1..1..1..1....0..0..0..0....0..1..1..0....0..0..0..0 %e A207119 ..1..0..0..0....1..1..1..0....0..0..0..0....0..0..0..0....1..0..1..1 %K A207119 nonn %O A207119 1,1 %A A207119 _R. H. Hardin_ Feb 15 2012