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 A207414 #7 Jul 22 2025 20:23:21 %S A207414 6,36,92,241,720,1889,4719,12102,30414,74588,182737,445468,1075185, %T A207414 2583413,6187826,14753420,35052328,83069841,196345572,462972905, %U A207414 1089545883,2559508250,6002666694,14057272936,32876868289,76799290072 %N A207414 Number of nX3 0..1 arrays avoiding 0 0 1 and 0 1 0 horizontally and 0 1 1 and 1 0 1 vertically. %C A207414 Column 3 of A207419 %H A207414 R. H. Hardin, <a href="/A207414/b207414.txt">Table of n, a(n) for n = 1..210</a> %F A207414 Empirical: a(n) = 4*a(n-1) -4*a(n-2) +7*a(n-3) -21*a(n-4) +7*a(n-5) -a(n-6) +33*a(n-7) +7*a(n-8) -13*a(n-9) -35*a(n-10) -7*a(n-11) +9*a(n-12) +17*a(n-13) +4*a(n-14) -3*a(n-15) -3*a(n-16) %e A207414 Some solutions for n=4 %e A207414 ..1..0..1....1..0..0....0..1..1....0..0..0....1..0..0....1..1..1....0..1..1 %e A207414 ..0..1..1....0..0..0....0..1..1....0..1..1....0..1..1....1..1..1....1..0..0 %e A207414 ..0..0..0....0..1..1....0..1..1....0..0..0....0..0..0....0..1..1....0..0..0 %e A207414 ..1..0..0....0..0..0....1..1..1....0..0..0....0..0..0....0..1..1....0..0..0 %K A207414 nonn %O A207414 1,1 %A A207414 _R. H. Hardin_ Feb 17 2012