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A199142 Number of n X 1 0..3 arrays with values 0..3 introduced in row major order and each element equal to one or two horizontal and vertical neighbors. 3
0, 1, 1, 2, 3, 6, 11, 23, 47, 102, 221, 492, 1099, 2485, 5637, 12858, 29391, 67354, 154539, 355003, 816035, 1876862, 4318201, 9937840, 22874731, 52659593, 121237417, 279141170, 642732027, 1479959118, 3407837387, 7847200511 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

COMMENTS

Column 1 of A199149.

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..200

FORMULA

Empirical: a(n) = 3*a(n-1) + a(n-2) - 7*a(n-3) + a(n-4) + 3*a(n-5) for n>6.

Empirical g.f.: x^2*(1 - 2*x - 2*x^2 + 3*x^3 + x^4) / ((1 - x)*(1 - x - x^2)*(1 - x - 3*x^2)). - Colin Barker, Feb 22 2018

EXAMPLE

Some solutions for n=8:

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0

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

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

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

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

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

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

CROSSREFS

Cf. A199149.

Sequence in context: A036656 A001190 A274937 * A090344 A277795 A198662

Adjacent sequences:  A199139 A199140 A199141 * A199143 A199144 A199145

KEYWORD

nonn

AUTHOR

R. H. Hardin, Nov 03 2011

STATUS

approved

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Last modified April 19 07:05 EDT 2018. Contains 302673 sequences. (Running on oeis4.)