

A281200


Number of n X 3 0..1 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards.


1



1, 14, 56, 168, 448, 1120, 2688, 6272, 14336, 32256, 71680, 157696, 344064, 745472, 1605632, 3440640, 7340032, 15597568, 33030144, 69730304, 146800640, 308281344, 645922816, 1350565888, 2818572288, 5872025600, 12213813248, 25367150592
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OFFSET

1,2


LINKS



FORMULA

Empirical: a(n) = 4*a(n1)  4*a(n2) for n>3.
G.f.: x*(1 + 10*x + 4*x^2) / (1  2*x)^2.
a(n) = 7*2^(n1) * (n1) for n>1.
(End)


EXAMPLE

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


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



