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 A207422 #7 Jul 22 2025 20:24:26 %S A207422 9,81,361,1521,6889,29929,127449,546121,2337841,9979281,42601729, %T A207422 181899169,776458225,3314189761,14146485721,60382741441,257733905625, %U A207422 1100096811025,4695589958761,20042356043161,85547497157721 %N A207422 Number of nX4 0..1 arrays avoiding 0 0 0 and 0 1 0 horizontally and 0 0 1 and 0 1 0 vertically. %C A207422 Column 4 of A207426 %H A207422 R. H. Hardin, <a href="/A207422/b207422.txt">Table of n, a(n) for n = 1..210</a> %F A207422 Empirical: a(n) = 4*a(n-1) +a(n-2) +8*a(n-3) -21*a(n-4) -46*a(n-5) -6*a(n-6) +35*a(n-7) +49*a(n-8) +19*a(n-9) -16*a(n-10) -21*a(n-11) -4*a(n-13) -2*a(n-14) +a(n-15) %e A207422 Some solutions for n=4 %e A207422 ..1..0..0..1....1..0..1..1....1..0..1..1....0..1..1..1....1..0..0..1 %e A207422 ..0..1..1..0....0..0..1..1....0..1..1..1....1..0..0..1....1..0..1..1 %e A207422 ..1..1..1..1....1..0..1..1....0..1..1..1....1..0..0..1....0..0..1..1 %e A207422 ..1..1..1..1....1..0..0..1....0..0..1..1....1..0..0..1....1..0..0..1 %K A207422 nonn %O A207422 1,1 %A A207422 _R. H. Hardin_ Feb 17 2012