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A281654 Number of 2 X n 0..2 arrays with no element equal to more than one of its horizontal, diagonal or antidiagonal neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards. 1
0, 4, 70, 400, 2128, 10512, 49352, 225024, 1003104, 4395200, 19006304, 81319168, 344886784, 1452055808, 6075680384, 25286555648, 104754555392, 432208419840, 1776869555712, 7281672187904, 29755307585536, 121277018935296 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

FORMULA

Empirical: a(n) = 8*a(n-1) - 20*a(n-2) + 32*a(n-3) - 84*a(n-4) + 96*a(n-5) - 96*a(n-6) + 128*a(n-7) - 64*a(n-8) for n>9.

Empirical g.f.: 2*x^2*(2 + 19*x - 40*x^2 + 100*x^3 - 208*x^4 + 256*x^5 - 192*x^6 + 64*x^7) / (1 - 4*x + 2*x^2 - 8*x^3 + 8*x^4)^2. - Colin Barker, Feb 20 2019

EXAMPLE

Some solutions for n=4:

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

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

CROSSREFS

Row 2 of A281653.

Sequence in context: A278553 A101841 A274873 * A222309 A061609 A301586

Adjacent sequences:  A281651 A281652 A281653 * A281655 A281656 A281657

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 26 2017

STATUS

approved

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Last modified December 1 05:33 EST 2021. Contains 349426 sequences. (Running on oeis4.)