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A204078 Number of nX2 0..3 arrays with every element neighboring horizontally or vertically both a 0 and a 1. 1
0, 4, 4, 16, 100, 324, 1296, 5476, 21316, 85264, 343396, 1368900, 5475600, 21921124, 87647044, 350588176, 1402502500, 5609710404, 22438841616, 89756564836, 359023862596, 1436095450384, 5744391388516, 22977546380100, 91910185520400 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 2 of A204084.

LINKS

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

FORMULA

Empirical: a(n) = 2*a(n-1) +4*a(n-2) +17*a(n-3) -2*a(n-4) -4*a(n-5) -16*a(n-6)

Empirical: a(n) = 4*round(2^n/7)^2  - Mark van Hoeij, May 14 2013

Empirical g.f.: 4*x^2*(1 - x - 2*x^2 - 4*x^3) / ((1 - x)*(1 - 4*x)*(1 + x + x^2)*(1 + 2*x + 4*x^2)). - Colin Barker, Jun 06 2018

EXAMPLE

Some solutions for n=5:

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

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

..2..1....2..2....0..3....1..0....1..1....1..0....1..1....1..0....3..3....0..2

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

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

CROSSREFS

Cf. A204084.

Sequence in context: A203101 A060691 A075225 * A284494 A091541 A094354

Adjacent sequences:  A204075 A204076 A204077 * A204079 A204080 A204081

KEYWORD

nonn

AUTHOR

R. H. Hardin, Jan 10 2012

STATUS

approved

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Last modified June 25 11:36 EDT 2018. Contains 311897 sequences. (Running on oeis4.)