A302000 Number of 3Xn 0..1 arrays with every element equal to 1, 2 or 4 horizontally or antidiagonally adjacent elements, with upper left element zero.

0, 5, 5, 26, 84, 309, 1108, 3979, 14314, 51440, 185083, 665473, 2393298, 8606453, 30950505, 111303112, 400265922, 1439423515, 5176415456, 18615274437, 66943726862, 240741120250, 865746384343, 3113372499381, 11196221683404

Offset: 1

Author

R. H. Hardin, Mar 30 2018

Keywords

• nonn

Comments

Row 3 of A301999.

Examples

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

Links

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

Crossrefs

Cf. A301999.

Formula

Empirical: a(n) = 2*a(n-1) +6*a(n-2) -2*a(n-4) +2*a(n-5) -9*a(n-6) -50*a(n-7) -37*a(n-8) +34*a(n-9) +43*a(n-10) -16*a(n-11) +15*a(n-12) +18*a(n-13) -7*a(n-14) -2*a(n-16) +4*a(n-17) -6*a(n-18) +a(n-20)