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A276293 Number of n X 2 0..2 arrays with no element equal to any value at offset (-2,-1) (-1,1) or (0,-1) and new values introduced in order 0..2. 1
1, 4, 11, 31, 88, 250, 710, 2016, 5724, 16252, 46144, 131016, 371992, 1056192, 2998832, 8514544, 24175232, 68640416, 194889824, 553348096, 1571113920, 4460842944, 12665612288, 35961305216, 102104457600, 289903834112 (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) = 4*a(n-1) - 4*a(n-2) + 2*a(n-3) for n>4.

Empirical g.f.: x*(1 - x^2 + x^3) / (1 - 4*x + 4*x^2 - 2*x^3). - Colin Barker, Feb 05 2019

EXAMPLE

Some solutions for n=4:

..0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1. .0..1

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

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

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

CROSSREFS

Column 2 of A276299.

Sequence in context: A298300 A027115 A077995 * A282856 A296572 A176573

Adjacent sequences:  A276290 A276291 A276292 * A276294 A276295 A276296

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 28 2016

STATUS

approved

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Last modified August 20 07:48 EDT 2019. Contains 326143 sequences. (Running on oeis4.)