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 A207903 #7 Jul 22 2025 20:57:49 %S A207903 6,36,102,261,611,1278,2625,5134,9798,18414,33947,62049,112332,201925, %T A207903 361298,643452,1142526,2023513,3576387,6311690,11124765,19589642, %U A207903 34469830,60616350,106548039,187215857,328865096,577561897,1014154398 %N A207903 Number of nX3 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 0 and 0 1 1 vertically. %C A207903 Column 3 of A207908 %H A207903 R. H. Hardin, <a href="/A207903/b207903.txt">Table of n, a(n) for n = 1..210</a> %F A207903 Empirical: a(n) = 3*a(n-1) -4*a(n-3) -5*a(n-4) +9*a(n-5) +3*a(n-6) -2*a(n-7) -5*a(n-8) +2*a(n-9) -2*a(n-10) +a(n-11) +a(n-12) +a(n-13) -a(n-14) %e A207903 Some solutions for n=4 %e A207903 ..0..0..1....0..1..1....1..0..0....0..1..1....0..0..1....0..1..1....1..0..0 %e A207903 ..1..0..0....1..1..0....0..1..1....1..0..0....1..0..1....1..0..1....0..0..1 %e A207903 ..0..1..1....0..0..1....1..0..0....0..0..1....0..1..1....0..1..1....1..1..0 %e A207903 ..1..0..0....1..0..0....0..0..1....1..1..0....0..0..1....1..0..1....0..0..1 %K A207903 nonn %O A207903 1,1 %A A207903 _R. H. Hardin_ Feb 21 2012