A301842 - OEIS

%I #4 Mar 27 2018 14:32:10

%S 2,8,25,81,263,855,2778,9027,29333,95316,309725,1006437,3270370,

%T 10626915,34531665,112209036,364618033,1184809305,3849982618,

%U 12510339087,40651763813,132096011916,429239834325,1394794836717,4532320816850

%N Number of 2Xn 0..1 arrays with every element equal to 0, 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero.

%C Row 2 of A301841.

%H R. H. Hardin, <a href="/A301842/b301842.txt">Table of n, a(n) for n = 1..210</a>

%F Empirical: a(n) = 3*a(n-1) +a(n-2) -2*a(n-4) for n>6

%e Some solutions for n=5

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

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

%Y Cf. A301841.

%K nonn

%O 1,1

%A _R. H. Hardin_, Mar 27 2018