

A269188


Number of n X 2 0..3 arrays with some element plus some horizontally, diagonally, antidiagonally or vertically adjacent neighbor totalling three no more than once.


1



16, 108, 708, 4476, 27684, 168252, 1008804, 5983164, 35170980, 205214268, 1189853604, 6861684156, 39384946596, 225136169532, 1282284719268, 7279841963964, 41210177357988, 232678853273148, 1310648830057380
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OFFSET

1,1


LINKS

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


FORMULA

Empirical: a(n) = 10*a(n1)  21*a(n2)  20*a(n3)  4*a(n4) for n>5.
Empirical g.f.: 4*x*(4  13*x  9*x^2  4*x^3 + 4*x^4) / (1  5*x  2*x^2)^2.  Colin Barker, Jan 19 2019


EXAMPLE

Some solutions for n=4:
..0..0. .2..0. .2..2. .1..3. .3..2. .1..3. .2..2. .0..2. .3..2. .0..0
..1..1. .2..2. .3..0. .3..2. .2..3. .1..0. .0..3. .0..1. .1..3. .1..2
..1..0. .2..2. .1..1. .2..3. .2..2. .0..0. .1..1. .0..0. .1..1. .3..3
..2..0. .0..0. .1..0. .2..3. .0..2. .2..2. .3..3. .1..0. .3..3. .1..1


CROSSREFS

Column 2 of A269194.
Sequence in context: A260357 A056001 A163725 * A165558 A337391 A250425
Adjacent sequences: A269185 A269186 A269187 * A269189 A269190 A269191


KEYWORD

nonn


AUTHOR

R. H. Hardin, Feb 20 2016


STATUS

approved



