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A280118 Number of n X 2 0..2 arrays with no element unequal to a strict majority of its horizontal, vertical and antidiagonal neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards. 1
0, 4, 8, 28, 80, 252, 776, 2356, 7200, 21836, 66104, 199652, 601424, 1808252, 5426024, 16253460, 48608384, 145152940, 432853144, 1289129028, 3834701744, 11394112476, 33820033480, 100286009972, 297101633248, 879410116620, 2600884035320 (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) = 2*a(n-1) + 7*a(n-2) - 24*a(n-4) - 32*a(n-5) - 16*a(n-6) for n>8.

Empirical g.f.: 4*x^2*(1 - 4*x^2 - 8*x^3 - 2*x^4 + 8*x^5 + 8*x^6) / (1 - x - 4*x^2 - 4*x^3)^2. - Colin Barker, Feb 12 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 2 of A280124.

Sequence in context: A189546 A059480 A105723 * A143555 A025234 A075308

Adjacent sequences:  A280115 A280116 A280117 * A280119 A280120 A280121

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 26 2016

STATUS

approved

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Last modified December 4 16:05 EST 2020. Contains 338930 sequences. (Running on oeis4.)