A208841 - OEIS

%I #9 Nov 05 2014 17:55:04

%S 9,81,171,855,2421,9801,31419,116919,394965,1419849,4902939,17375031,

%T 60551541,213310665,746231931,2622329271,9188418069,32255749449,

%U 113096449755,396852637239,1391845926069,4883081614281,17127968887611

%N Number of 4 X n 0..1 arrays avoiding 0 0 0 and 0 0 1 horizontally and 0 1 1 and 1 1 0 vertically.

%C Row 4 of A208840.

%H R. H. Hardin, <a href="/A208841/b208841.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 2*a(n-1) +7*a(n-2) -6*a(n-3).

%e Some solutions for n=4:

%e ..1..1..1..1....0..1..1..1....0..1..1..0....0..1..1..0....1..0..1..1

%e ..0..1..0..1....0..1..0..1....0..1..1..1....1..1..0..0....0..1..1..0

%e ..1..1..1..1....0..1..0..1....1..1..1..0....0..1..0..1....1..0..1..1

%e ..0..1..0..1....0..1..1..1....0..1..1..1....0..1..1..0....0..1..1..0

%Y Cf. A208840.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 01 2012