A316688 - OEIS

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A316688

Number of nX3 0..1 arrays with every element unequal to 0, 1, 2, 6, 7 or 8 king-move adjacent elements, with upper left element zero.

4, 3, 8, 9, 21, 42, 81, 165, 330, 657, 1317, 2634, 5265, 10533, 21066, 42129, 84261, 168522, 337041, 674085, 1348170, 2696337, 5392677, 10785354, 21570705, 43141413, 86282826, 172565649, 345131301, 690262602, 1380525201, 2761050405, 5522100810

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OFFSET

1,1

COMMENTS

Column 3 of A316693.

LINKS

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

FORMULA

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

EXAMPLE

Some solutions for n=5

..0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0. .0..0..0

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

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

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

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

CROSSREFS

Cf. A316693.

Sequence in context: A198576 A368551 A175047 * A309517 A105185 A357587

Adjacent sequences: A316685 A316686 A316687 * A316689 A316690 A316691

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jul 10 2018

STATUS

approved