cp's OEIS Frontend

A268622 Number of n X 2 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.

%I A268622 #7 Mar 21 2018 09:46:40
%S A268622 9,42,174,666,2430,8586,29646,100602,336798,1115370,3661038,11927898,
%T A268622 38618046,124357194,398580750,1272269754,4046391774,12827922858,
%U A268622 40550011182,127848761370,402142467582,1262215953162,3954013510734
%N A268622 Number of n X 2 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once.
%C A268622 Column 2 of A268628.
%H A268622 R. H. Hardin, <a href="/A268622/b268622.txt">Table of n, a(n) for n = 1..210</a>
%F A268622 Empirical: a(n) = 6*a(n-1) - 9*a(n-2) for n>3.
%F A268622 Conjectures from _Colin Barker_, Mar 21 2018: (Start)
%F A268622 G.f.: 3*x*(3 - x)*(1 - x) / (1 - 3*x)^2.
%F A268622 a(n) = 2*3^(n-2)*(5+8*n) for n>1.
%F A268622 (End)
%e A268622 Some solutions for n=8:
%e A268622 ..1..0. .0..1. .2..1. .1..2. .2..2. .0..1. .0..0. .0..0. .1..0. .1..0
%e A268622 ..2..2. .1..0. .1..0. .2..1. .2..2. .1..0. .0..1. .0..1. .2..2. .0..0
%e A268622 ..2..1. .2..1. .2..1. .1..2. .1..2. .2..1. .0..0. .0..0. .1..2. .1..2
%e A268622 ..2..2. .2..2. .1..0. .2..2. .2..2. .2..2. .1..0. .0..0. .0..1. .2..1
%e A268622 ..2..1. .1..2. .2..1. .2..2. .2..1. .2..1. .0..1. .0..0. .1..0. .1..2
%e A268622 ..2..2. .2..2. .1..2. .2..1. .2..2. .2..0. .0..0. .1..0. .2..1. .2..2
%e A268622 ..1..2. .1..2. .1..2. .1..2. .0..1. .1..0. .1..0. .2..2. .2..2. .1..2
%e A268622 ..2..2. .0..0. .0..1. .2..1. .1..2. .0..0. .0..1. .1..2. .1..2. .0..1
%Y A268622 Cf. A268628.
%K A268622 nonn
%O A268622 1,1
%A A268622 _R. H. Hardin_, Feb 09 2016