A301779 Number of nX3 0..1 arrays with every element equal to 0, 1, 2 or 3 horizontally or vertically adjacent elements, with upper left element zero.

4, 32, 240, 1808, 13616, 102544, 772272, 5816080, 43801648, 329875856, 2484337584, 18709866512, 140906415920, 1061184377488, 7991916306096, 60188151652624, 453284726792752, 3413745694159760, 25709358766289328, 193620494140664336

Offset: 1

Author

R. H. Hardin, Mar 26 2018

Keywords

• nonn

Comments

Column 3 of A301784.

Examples

			Some solutions for n=5
..0..1..0. .0..0..0. .0..0..1. .0..0..1. .0..1..0. .0..1..1. .0..0..1
..1..1..0. .0..1..0. .1..1..1. .0..0..0. .1..1..1. .1..0..0. .0..0..1
..0..0..0. .1..0..1. .0..0..1. .1..1..0. .1..0..0. .0..1..1. .0..0..0
..1..0..1. .1..1..0. .1..1..0. .1..1..1. .0..1..1. .0..1..0. .0..1..0
..0..0..1. .0..0..0. .1..0..1. .1..0..0. .0..0..1. .1..0..0. .1..0..0
		

Links

• R. H. Hardin, Table of n, a(n) for n = 1..210

Crossrefs

Cf. A301784.

Formula

Empirical: a(n) = 7*a(n-1) +4*a(n-2)