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A234779 Number of (n+1) X (1+1) 0..3 arrays with no adjacent elements equal and with each 2 X 2 subblock having the number of clockwise edge increases equal to the number of counterclockwise edge increases. 1
76, 484, 3084, 19652, 125228, 797988, 5085004, 32403076, 206481516, 1315758308, 8384382092, 53427641412, 340455961516, 2169481164964, 13824544308684, 88093885500932, 561359021271788, 3577137606898788, 22794527163204364 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

R. H. Hardin, Table of n, a(n) for n = 1..210

FORMULA

Empirical: a(n) = 7*a(n-1) - 4*a(n-2).

Conjectures from Colin Barker, Oct 16 2018: (Start)

G.f.: 4*x*(19 - 12*x) / (1 - 7*x + 4*x^2).

a(n) = (2^(1-n)*((7-sqrt(33))^n*(-17+3*sqrt(33)) + (7+sqrt(33))^n*(17+3*sqrt(33)))) / sqrt(33).

(End)

EXAMPLE

Some solutions for n=5:

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

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

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

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

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

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

CROSSREFS

Column 1 of A234786.

Sequence in context: A205919 A238918 A234786 * A264475 A262790 A184680

Adjacent sequences:  A234776 A234777 A234778 * A234780 A234781 A234782

KEYWORD

nonn

AUTHOR

R. H. Hardin, Dec 30 2013

STATUS

approved

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Last modified October 16 20:23 EDT 2019. Contains 328103 sequences. (Running on oeis4.)