A268888 Number of 3 X n binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once.

0, 20, 84, 501, 2190, 9996, 42362, 178400, 732378, 2974934, 11933578, 47466417, 187325260, 734639334, 2865135348, 11121381104, 42989239524, 165564387000, 635557701344, 2432620417837, 9286486715514, 35366757558512, 134400104565934

Offset: 1

Author

R. H. Hardin, Feb 15 2016

Keywords

• nonn

Examples

			Some solutions for n=4:
..0..0..1..0. .0..0..0..0. .0..0..0..1. .0..0..0..0. .0..1..0..1
..1..0..0..0. .0..0..0..1. .1..1..0..1. .0..0..1..1. .0..0..0..1
..1..0..1..1. .1..1..0..0. .0..0..0..0. .1..0..0..1. .0..0..1..0
		

Links

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

Crossrefs

Row 3 of A268886.

Formula

Empirical: a(n) = 3*a(n-1) + 12*a(n-2) - 16*a(n-3) - 62*a(n-4) - 34*a(n-5) + 16*a(n-6) + 12*a(n-7) - a(n-8) - a(n-9).

Empirical g.f.: x^2*(2 - x)*(10 + 17*x + 13*x^2 + 6*x^3 + 2*x^4) / ((1 + x)*(1 - 2*x - 6*x^2 + x^4)^2). - Colin Barker, Jan 15 2019