A199143 - OEIS

%I #5 Mar 31 2012 12:36:35

%S 1,3,13,65,393,2539,16866,113432,766473,5188597,35148945,238173743,

%T 1614066774,10938730576,74134306725,502428413393,3405102418833,

%U 23077383280435,156402287318610,1059984943413152,7183834447992225

%N Number of nX2 0..3 arrays with values 0..3 introduced in row major order and each element equal to one or two horizontal and vertical neighbors

%C Column 2 of A199149

%H R. H. Hardin, <a href="/A199143/b199143.txt">Table of n, a(n) for n = 1..200</a>

%F Empirical: a(n) = 7*a(n-1) +2*a(n-2) -16*a(n-3) -49*a(n-4) -35*a(n-5) +56*a(n-6) +54*a(n-7) +45*a(n-8) -27*a(n-9) for n>11

%e Some solutions for n=4

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

%e ..0..1....0..0....1..2....1..0....0..1....0..1....1..0....0..1....0..1....0..1

%e ..1..1....1..1....1..2....1..0....1..1....0..1....1..0....1..2....0..0....0..1

%e ..0..0....0..0....1..1....1..1....2..2....1..1....1..0....1..2....1..1....0..1

%K nonn

%O 1,2

%A _R. H. Hardin_ Nov 03 2011