

A202882


Number of n X 1 0..2 arrays with every nonzero element less than or equal to some horizontal or vertical neighbor.


8



1, 3, 9, 22, 51, 121, 292, 704, 1691, 4059, 9749, 23422, 56268, 135166, 324692, 779977, 1873673, 4500958, 10812237, 25973244, 62393157, 149881402, 360046432, 864906711, 2077686532, 4991036946, 11989513056, 28801314179, 69186771332
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OFFSET

1,2


LINKS



FORMULA

Empirical: a(n) = 3*a(n1) 3*a(n2) +4*a(n3) a(n4) +a(n5).
Empirical: G.f.: x*(1+3*x^2+x^4)/(1+3*x3*x^2+4*x^3x^4+x^5).  R. J. Mathar, Jul 09 2017


EXAMPLE

Some solutions for n=5
..2....2....1....0....2....2....0....1....0....1....1....0....2....1....0....2
..2....2....1....1....2....2....2....1....2....2....1....0....2....2....1....2
..0....1....1....2....0....2....2....0....2....2....1....1....1....2....1....0
..0....1....1....2....1....1....2....0....0....0....2....1....2....2....2....2
..0....0....1....2....1....1....1....0....0....0....2....1....2....0....2....2


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



