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A268622 Number of n X 2 0..2 arrays with some element plus some horizontally or vertically adjacent neighbor totalling two no more than once. 2
9, 42, 174, 666, 2430, 8586, 29646, 100602, 336798, 1115370, 3661038, 11927898, 38618046, 124357194, 398580750, 1272269754, 4046391774, 12827922858, 40550011182, 127848761370, 402142467582, 1262215953162, 3954013510734 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 2 of A268628.

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) - 9*a(n-2) for n>3.

Conjectures from Colin Barker, Mar 21 2018: (Start)

G.f.: 3*x*(3 - x)*(1 - x) / (1 - 3*x)^2.

a(n) = 2*3^(n-2)*(5+8*n) for n>1.

(End)

EXAMPLE

Some solutions for n=8:

..1..0. .0..1. .2..1. .1..2. .2..2. .0..1. .0..0. .0..0. .1..0. .1..0

..2..2. .1..0. .1..0. .2..1. .2..2. .1..0. .0..1. .0..1. .2..2. .0..0

..2..1. .2..1. .2..1. .1..2. .1..2. .2..1. .0..0. .0..0. .1..2. .1..2

..2..2. .2..2. .1..0. .2..2. .2..2. .2..2. .1..0. .0..0. .0..1. .2..1

..2..1. .1..2. .2..1. .2..2. .2..1. .2..1. .0..1. .0..0. .1..0. .1..2

..2..2. .2..2. .1..2. .2..1. .2..2. .2..0. .0..0. .1..0. .2..1. .2..2

..1..2. .1..2. .1..2. .1..2. .0..1. .1..0. .1..0. .2..2. .2..2. .1..2

..2..2. .0..0. .0..1. .2..1. .1..2. .0..0. .0..1. .1..2. .1..2. .0..1

CROSSREFS

Cf. A268628.

Sequence in context: A268262 A293101 A084899 * A289364 A074443 A221425

Adjacent sequences:  A268619 A268620 A268621 * A268623 A268624 A268625

KEYWORD

nonn

AUTHOR

R. H. Hardin, Feb 09 2016

STATUS

approved

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Last modified September 24 18:55 EDT 2022. Contains 356949 sequences. (Running on oeis4.)