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A197469 Number of n X 2 0..4 arrays with each element x equal to the number its horizontal and vertical neighbors equal to 0,1,0,0,0 for x=0,1,2,3,4. 1
1, 2, 6, 12, 24, 50, 98, 194, 394, 786, 1562, 3138, 6282, 12530, 25082, 50210, 100330, 200658, 401498, 802818, 1605450, 3211442, 6422714, 12844514, 25690282, 51381138, 102759194, 205520322, 411044874, 822081650, 1644162938, 3288342434 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Every 0 is next to 0 0's, every 1 is next to 1 1's, every 2 is next to 2 0's, every 3 is next to 3 0's, every 4 is next to 4 0's.

Column 2 of A197475.

LINKS

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

FORMULA

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

Empirical g.f.: x*(1 + x + 4*x^2 + 2*x^3 + 4*x^4 + 2*x^5) / ((1 - 2*x)*(1 + x + 2*x^2)). - Colin Barker, May 12 2018

EXAMPLE

Some solutions for n=4:

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

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

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

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

CROSSREFS

Cf. A197475.

Sequence in context: A058295 A309841 A132176 * A133953 A122863 A170935

Adjacent sequences:  A197466 A197467 A197468 * A197470 A197471 A197472

KEYWORD

nonn

AUTHOR

R. H. Hardin, Oct 15 2011

STATUS

approved

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Last modified March 29 02:19 EDT 2020. Contains 333104 sequences. (Running on oeis4.)