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A268888 Number of 3 X n binary arrays with some element plus some horizontally or antidiagonally adjacent neighbor totalling two exactly once. 1
0, 20, 84, 501, 2190, 9996, 42362, 178400, 732378, 2974934, 11933578, 47466417, 187325260, 734639334, 2865135348, 11121381104, 42989239524, 165564387000, 635557701344, 2432620417837, 9286486715514, 35366757558512, 134400104565934 (list; graph; refs; listen; history; text; internal format)
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

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Last modified September 18 03:36 EDT 2021. Contains 347504 sequences. (Running on oeis4.)