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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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,3

LINKS

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

FORMULA

Empirical: a(n) = 9*a(n-1) - 30*a(n-2) + 45*a(n-3) - 30*a(n-4) + 9*a(n-5) - a(n-6).

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

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Last modified June 23 21:09 EDT 2021. Contains 345402 sequences. (Running on oeis4.)