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A232031 Number of (n+1) X (1+1) 0..1 arrays with every element equal to some horizontal, vertical or antidiagonal neighbor, with top left element zero. 4
3, 11, 37, 129, 450, 1568, 5464, 19041, 66354, 231230, 805789, 2808009, 9785334, 34099877, 118831060, 414101811, 1443059667, 5028766229, 17524216333, 61068290730, 212810436816, 741600615908, 2584325664397, 9005843571858 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Column 1 of A232038.

LINKS

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

FORMULA

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

Empirical g.f.: x*(3 - x - x^2) / (1 - 4*x + 2*x^2 - x^3 + x^4). - Colin Barker, Mar 19 2018

EXAMPLE

Some solutions for n=7:

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

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

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

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

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

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

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

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

CROSSREFS

Cf. A232038.

Sequence in context: A046722 A214996 A180168 * A047102 A109000 A183511

Adjacent sequences:  A232028 A232029 A232030 * A232032 A232033 A232034

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 17 2013

STATUS

approved

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Last modified October 21 02:29 EDT 2021. Contains 348141 sequences. (Running on oeis4.)