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A246481 Number of length 2+3 0..n arrays with no pair in any consecutive four terms totalling exactly n. 1
2, 14, 132, 484, 1734, 4386, 10376, 20840, 39690, 68950, 115212, 181644, 278222, 409514, 589584, 824656, 1133586, 1524510, 2021780, 2635700, 3396822, 4317874, 5436312, 6767544, 8356634, 10221926, 12416796, 14962780, 17922270, 21320250 (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) = 3*a(n-1) - 8*a(n-3) + 6*a(n-4) + 6*a(n-5) - 8*a(n-6) + 3*a(n-8) - a(n-9).

Conjectures from Colin Barker, Nov 06 2018: (Start)

G.f.: 2*x*(1 + 4*x + 45*x^2 + 52*x^3 + 191*x^4 + 72*x^5 + 115*x^6) / ((1 - x)^6*(1 + x)^3).

a(n) = 5*n - 11*n^2 + 10*n^3 - 4*n^4 + n^5 for n even.

a(n) = 9 - 10*n - 4*n^2 + 10*n^3 - 4*n^4 + n^5 for n odd.

(End)

EXAMPLE

Some solutions for n=6:

..0....1....0....0....3....3....3....4....6....6....5....2....4....1....2....0

..2....0....0....5....6....1....2....3....3....1....0....0....0....1....5....4

..0....4....0....4....6....4....6....4....4....3....5....0....5....2....6....1

..2....4....3....5....6....6....2....4....4....6....0....0....3....0....6....4

..0....1....2....0....1....6....3....6....0....2....4....0....5....2....6....1

CROSSREFS

Row 2 of A246479.

Sequence in context: A235347 A235352 A146971 * A048990 A089602 A052641

Adjacent sequences:  A246478 A246479 A246480 * A246482 A246483 A246484

KEYWORD

nonn

AUTHOR

R. H. Hardin, Aug 27 2014

STATUS

approved

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Last modified January 19 04:03 EST 2019. Contains 319299 sequences. (Running on oeis4.)