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 A207307 #7 Jul 22 2025 20:16:53 %S A207307 8,64,200,643,1759,4939,14446,41505,118266,339548,975493,2795633, %T A207307 8015023,22994104,65948845,189120690,542403026,1555646545,4461518045, %U A207307 12795484071,36697414724,105247642363,301847990088,865695191094,2482800552095 %N A207307 Number of 4Xn 0..1 arrays avoiding 0 0 0 and 1 0 1 horizontally and 0 0 1 and 1 1 0 vertically. %C A207307 Row 4 of A207305 %H A207307 R. H. Hardin, <a href="/A207307/b207307.txt">Table of n, a(n) for n = 1..210</a> %F A207307 Empirical: a(n) = a(n-1) +2*a(n-2) +8*a(n-3) +7*a(n-4) -2*a(n-5) -10*a(n-6) -10*a(n-7) -a(n-8) +3*a(n-9) +4*a(n-10) +a(n-11) -a(n-13) for n>14 %e A207307 Some solutions for n=4 %e A207307 ..1..0..0..1....0..0..1..0....1..1..0..0....0..0..1..1....1..1..1..1 %e A207307 ..0..1..1..0....1..0..0..1....1..1..0..0....1..0..0..1....1..1..1..1 %e A207307 ..1..0..0..1....0..0..1..0....1..1..0..0....0..0..1..1....1..1..1..1 %e A207307 ..1..1..1..1....1..0..0..1....1..1..0..0....0..0..1..1....1..1..1..1 %K A207307 nonn %O A207307 1,1 %A A207307 _R. H. Hardin_ Feb 16 2012