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A274745 Number of n X 4 0..2 arrays with no element equal to any value at offset (-1,-2) (0,-1) or (-1,0) and new values introduced in order 0..2. 1
4, 22, 133, 813, 4967, 30349, 185435, 1133025, 6922887, 42299477, 258453699, 1579175897, 9648910127, 58955729261, 360224933899, 2201007512401, 13448358549783, 82170708943301, 502070597184787, 3067697574952457 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) + a(n-2) - 2*a(n-3) for n>4.

Empirical g.f.: x*(1 - x)*(4 + 2*x - x^2) / (1 - 6*x - x^2 + 2*x^3). - Colin Barker, Jan 30 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 4 of A274749.

Sequence in context: A292838 A193620 A321275 * A197657 A183280 A183281

Adjacent sequences:  A274742 A274743 A274744 * A274746 A274747 A274748

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 04 2016

STATUS

approved

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Last modified July 23 11:44 EDT 2019. Contains 325254 sequences. (Running on oeis4.)