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 A207237 #7 Jul 22 2025 20:11:15 %S A207237 6,36,102,287,882,2491,6759,18528,50244,134284,357919,951428,2517507, %T A207237 6644999,17514496,46087746,121122382,318060011,834615854,2188807497, %U A207237 5737757291,15035923244,39391026514,103174230894,270192214787 %N A207237 Number of nX3 0..1 arrays avoiding 0 0 0 and 0 1 1 horizontally and 0 0 1 and 0 1 0 vertically. %C A207237 Column 3 of A207242 %H A207237 R. H. Hardin, <a href="/A207237/b207237.txt">Table of n, a(n) for n = 1..210</a> %F A207237 Empirical: a(n) = 3*a(n-1) -a(n-2) +6*a(n-3) -12*a(n-4) -8*a(n-5) -10*a(n-6) +8*a(n-7) +13*a(n-8) +11*a(n-9) -2*a(n-10) -4*a(n-11) -4*a(n-12) +a(n-14) %e A207237 Some solutions for n=4 %e A207237 ..1..1..1....0..0..1....1..0..0....1..1..1....1..1..0....1..0..0....0..0..1 %e A207237 ..0..1..0....0..1..0....0..0..1....1..1..1....0..0..1....0..1..0....1..1..0 %e A207237 ..1..1..1....0..1..0....1..0..1....0..1..0....0..0..1....1..1..0....1..1..0 %e A207237 ..1..0..1....0..1..0....1..0..1....0..1..0....0..0..1....1..0..0....1..0..0 %K A207237 nonn %O A207237 1,1 %A A207237 _R. H. Hardin_ Feb 16 2012