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

1,2

Links

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

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

Example

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

Crossrefs

Row 3 of A268886.

Sequence in context: A172221 A006566 A205312 * A211158 A154077 A027849

Adjacent sequences: A268885 A268886 A268887 * A268889 A268890 A268891

Keyword

nonn

Author

R. H. Hardin, Feb 15 2016

Status

approved