A281320 - OEIS

A281320

Number of n X 2 0..2 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.

0, 2, 28, 304, 2976, 27488, 244544, 2119168, 18011136, 150809088, 1247857664, 10226274304, 83138240512, 671370043392, 5390483210240, 43066315243520, 342583723687936, 2714813886234624, 21440990518444032, 168825545758343168

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OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 16*a(n-1) - 72*a(n-2) + 64*a(n-3) - 16*a(n-4).

Empirical g.f.: 2*x^2*(1 - 2*x) / (1 - 8*x + 4*x^2)^2. - Colin Barker, Feb 18 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A281326.

Sequence in context: A230589 A097353 A092801 * A152280 A061629 A230130

Adjacent sequences: A281317 A281318 A281319 * A281321 A281322 A281323

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 20 2017

STATUS

approved