

A281050


Number of n X 2 0..1 arrays with no element equal to more than one of its horizontal and antidiagonal neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards.


1



0, 1, 6, 29, 122, 468, 1686, 5807, 19338, 62731, 199264, 622152, 1914780, 5821645, 17515566, 52221929, 154461110, 453654108, 1324053522, 3842768987, 11096398578, 31895230903, 91296545404, 260329675536, 739725018360, 2095147333465
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OFFSET

1,3


LINKS

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


FORMULA

Empirical: a(n) = 9*a(n1)  30*a(n2) + 45*a(n3)  30*a(n4) + 9*a(n5)  a(n6).
Empirical g.f.: x^2*(1  3*x + 5*x^2  4*x^3) / (1  3*x + x^2)^3.  Colin Barker, Feb 15 2019


EXAMPLE

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


CROSSREFS

Column 2 of A281056.
Sequence in context: A184130 A326805 A061648 * A267774 A243474 A111644
Adjacent sequences: A281047 A281048 A281049 * A281051 A281052 A281053


KEYWORD

nonn


AUTHOR

R. H. Hardin, Jan 13 2017


STATUS

approved



