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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 (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) = (2/3)*n^4 + (10/3)*n^3 - (5/3)*n^2 + (2/3)*n - 1.

Conjectures from Colin Barker, Sep 13 2018: (Start)

G.f.: x*(2 - x)*(1 + 11*x + 3*x^2 + x^3) / (1 - x)^5.

a(n) = 5*a(n-1) - 10*a(n-2) + 10*a(n-3) - 5*a(n-4) + a(n-5) 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

Row 4 of A229012.

Sequence in context: A273403 A291052 A267888 * A042059 A343830 A137626

Adjacent sequences:  A229011 A229012 A229013 * A229015 A229016 A229017

KEYWORD

nonn

AUTHOR

R. H. Hardin, Sep 10 2013

STATUS

approved

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Last modified September 25 20:01 EDT 2021. Contains 347659 sequences. (Running on oeis4.)