

A242543


Number of length n+3 0..2 arrays with no four elements in a row with pattern aabb (possibly a=b) and new values 0..2 introduced in 0..2 order


1



12, 32, 88, 242, 660, 1800, 4920, 13448, 36736, 100352, 274176, 749088, 2046528, 5591168, 15275392, 41733248, 114017280, 311500800, 851036160, 2325074432, 6352221184, 17354590208, 47413622784, 129536428032, 353900101632
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OFFSET

1,1


COMMENTS



LINKS



FORMULA

Empirical: a(n) = 2*a(n1) +4*a(n3) +4*a(n4).
Empirical: G.f.: 2*x*(6+4*x+12*x^2+9*x^3) / ( (2*x^2+2*x1)*(2*x^2+1) ).  R. J. Mathar, May 18 2014


EXAMPLE

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


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



