

A205737


Number of 2 X (n+1) 0..2 arrays with every 2 X 2 subblock having the same number of clockwise edge increases as its horizontal neighbors and no 2 X 2 subblock having the same number of counterclockwise edge increases as its vertical neighbors.


3



81, 369, 1764, 8655, 43155, 218034, 1112664, 5722236, 29600808, 153794865, 801658320, 4188664470, 21924195099, 114902238879, 602752637715, 3164061809547, 16617483609822, 87305419041021, 458806978246497
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OFFSET

1,1


COMMENTS



LINKS



FORMULA

Empirical: a(n) = 9*a(n1) 18*a(n2) 15*a(n3) +36*a(n4) 20*a(n5) +11*a(n6) 2*a(n7).
Empirical g.f.: 3*x*(27  120*x  33*x^2 + 212*x^3  123*x^4 + 75*x^5  14*x^6) / ((1  x)*(1  4*x + x^2  x^3)*(1  4*x  7*x^2 + 2*x^3)).  Colin Barker, Feb 23 2018


EXAMPLE

Some solutions for n=4:
..1..2..0..1..0....2..0..2..2..2....2..1..2..2..1....2..2..2..1..2
..0..2..1..2..1....0..0..2..1..2....0..1..1..1..1....1..1..1..1..1


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



