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A280309 Number of n X 1 0..2 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly two elements, and with new values introduced in order 0 sequentially upwards. 5
0, 0, 0, 1, 2, 9, 34, 124, 432, 1464, 4848, 15768, 50528, 159920, 500832, 1554304, 4785664, 14632704, 44465664, 134378112, 404089344, 1209699584, 3606669824, 10713166848, 31713660928, 93585811456, 275367776256, 808068888576 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,5

COMMENTS

Column 1 of A280313.

LINKS

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

FORMULA

Empirical: a(n) = 6*a(n-1) - 6*a(n-2) - 16*a(n-3) + 12*a(n-4) + 24*a(n-5) + 8*a(n-6) for n>10.

Empirical g.f.: x^4*(1 - 4*x + 3*x^2 + 8*x^3 - 6*x^4 - 12*x^5 - 4*x^6) / (1 - 2*x - 2*x^2)^3. - Colin Barker, Feb 19 2018

EXAMPLE

All solutions for n=6:

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

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

..0. .2. .0. .1. .1. .0. .1. .0. .0

..0. .2. .0. .1. .1. .1. .1. .0. .0

..1. .2. .1. .1. .1. .1. .1. .0. .1

..0. .2. .1. .0. .1. .1. .2. .0. .2

CROSSREFS

Cf. A280313.

Sequence in context: A000524 A289614 A120989 * A010763 A077234 A091526

Adjacent sequences:  A280306 A280307 A280308 * A280310 A280311 A280312

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 31 2016

STATUS

approved

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Last modified November 17 00:08 EST 2019. Contains 329209 sequences. (Running on oeis4.)