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A280439 Number of n X 7 0..1 arrays with no element equal to more than one of its horizontal and vertical neighbors, with the exception of exactly one element, and with new values introduced in order 0 sequentially upwards. 1
20, 120, 236, 386, 574, 834, 1211, 1784, 2684, 4128, 6478, 10334, 16693, 27208, 44620, 73470, 121278, 200490, 331695, 548936, 908476, 1503260, 2486766, 4112326, 6797929, 11232984, 18554156, 30634874, 50561854, 83419218, 137578403 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

FORMULA

Empirical: a(n) = 4*a(n-1) - 4*a(n-2) - 2*a(n-3) + 4*a(n-4) - a(n-6) for n>7.

Empirical g.f.: x*(20 + 40*x - 164*x^2 - 38*x^3 + 134*x^4 + 74*x^5 + 19*x^6) / ((1 - x)^2*(1 - x - x^2)^2). - Colin Barker, Feb 13 2019

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Column 7 of A280440.

Sequence in context: A121040 A044352 A044733 * A093566 A213223 A041770

Adjacent sequences:  A280436 A280437 A280438 * A280440 A280441 A280442

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 03 2017

STATUS

approved

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Last modified December 3 19:30 EST 2020. Contains 338917 sequences. (Running on oeis4.)