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A196423 Number of n X 1 0..4 arrays with each element equal to the number its horizontal and vertical neighbors less than itself. 5
1, 3, 5, 11, 26, 55, 119, 263, 573, 1248, 2729, 5959, 13005, 28399, 62010, 135383, 295595, 645407, 1409161, 3076736, 6717713, 14667339, 32024421, 69921635, 152665786, 333328023, 727783135, 1589030151, 3469463141, 7575170720 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Column 1 of A196430.

LINKS

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

FORMULA

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

Empirical: G.f. -x*(1+x)^2 / ( -1+x+x^2+3*x^3+x^4 ). - R. J. Mathar, Jul 25 2012

EXAMPLE

All solutions for n=3:

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

..0....0....2....0....0

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

CROSSREFS

Cf. A196430.

Sequence in context: A027050 A240148 A109249 * A320177 A289468 A289534

Adjacent sequences:  A196420 A196421 A196422 * A196424 A196425 A196426

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 02 2011

STATUS

approved

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Last modified August 5 10:01 EDT 2021. Contains 346464 sequences. (Running on oeis4.)