A301843 Number of 3Xn 0..1 arrays with every element equal to 0, 1 or 2 horizontally or antidiagonally adjacent elements, with upper left element zero.

4, 32, 139, 678, 3182, 15199, 72514, 346244, 1653214, 7893443, 37688062, 179946317, 859175558, 4102237937, 19586633161, 93518758201, 446516665710, 2131948036306, 10179244758257, 48602040050313, 232056341426270, 1107981178164225

Offset: 1

Author

R. H. Hardin, Mar 27 2018

Keywords

• nonn

Comments

Row 3 of A301841.

Examples

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

Links

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

Crossrefs

Cf. A301841.

Formula

Empirical: a(n) = 4*a(n-1) +3*a(n-2) +3*a(n-3) +2*a(n-4) -2*a(n-5) +2*a(n-6) -7*a(n-7) -3*a(n-8) +5*a(n-9) -4*a(n-10) -3*a(n-11) +a(n-12) for n>14