

A229014


Number of arrays of median of three adjacent elements of some length 6 0..n array, with no adjacent equal elements in the latter.


1



2, 31, 130, 359, 794, 1527, 2666, 4335, 6674, 9839, 14002, 19351, 26090, 34439, 44634, 56927, 71586, 88895, 109154, 132679, 159802, 190871, 226250, 266319, 311474, 362127, 418706, 481655, 551434, 628519, 713402, 806591, 908610, 1019999, 1141314
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OFFSET

1,1


LINKS



FORMULA

Empirical: a(n) = (2/3)*n^4 + (10/3)*n^3  (5/3)*n^2 + (2/3)*n  1.
G.f.: x*(2  x)*(1 + 11*x + 3*x^2 + x^3) / (1  x)^5.
a(n) = 5*a(n1)  10*a(n2) + 10*a(n3)  5*a(n4) + a(n5) for n>5.
(End)


EXAMPLE

Some solutions for n=4:
..2....3....2....3....3....1....3....0....0....0....2....2....4....3....1....2
..0....3....4....3....3....1....2....3....1....2....1....4....1....2....3....0
..2....0....2....1....3....3....3....2....2....3....2....0....1....4....3....3
..3....4....2....3....3....1....1....2....2....3....1....2....0....1....4....3


CROSSREFS



KEYWORD

nonn


AUTHOR



STATUS

approved



