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A217631 Number of nX2 arrays of the minimum value of corresponding elements and their horizontal and vertical neighbors in a random 0..1 nX2 array 6
0, 2, 6, 16, 38, 98, 244, 614, 1542, 3872, 9726, 24426, 61348, 154078, 386974, 971904, 2440982, 6130642, 15397396, 38671286, 97124758, 243933408, 612650254, 1538699994, 3864517572, 9705918062, 24376870766, 61223660096, 153766108518 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

COMMENTS

Also, number of maximal independent sets in the 3-dimensional (2, 2, n) grid graph. [Euler et al.] - N. J. A. Sloane, Nov 21 2013

Column 2 of A217637.

LINKS

R. H. Hardin, Table of n, a(n) for n = 0..210

R. Euler, P. Oleksik, Z. Skupien, Counting Maximal Distance-Independent Sets in Grid Graphs, Discussiones Mathematicae Graph Theory. Volume 33, Issue 3, Pages 531-557, ISSN (Print) 2083-5892, July 2013; http://www.degruyter.com/view/j/dmgt.2013.33.issue-3/dmgt.1707/dmgt.1707.xml

FORMULA

G.f. = (2*x+4*x^2+4*x^3)/(1-x-3*x^2-2*x^3). [Euler et al.] - N. J. A. Sloane, Nov 21 2013

Empirical: a(n) = a(n-1) + 3*a(n-2) + 2*a(n-3). (Follows from g.f. - N. J. A. Sloane, Nov 21 2013)

EXAMPLE

Some solutions for n=3

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

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

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

CROSSREFS

Cf. A217632, A217637.

Sequence in context: A156616 A265758 A265107 * A046209 A285885 A273348

Adjacent sequences:  A217628 A217629 A217630 * A217632 A217633 A217634

KEYWORD

nonn

AUTHOR

R. H. Hardin Oct 09 2012

STATUS

approved

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Last modified March 20 09:50 EDT 2019. Contains 321345 sequences. (Running on oeis4.)