A246481 Number of length 2+3 0..n arrays with no pair in any consecutive four terms totalling exactly n.

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

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 A336960

Adjacent sequences: A246478 A246479 A246480 * A246482 A246483 A246484

Keyword

nonn

Author

R. H. Hardin, Aug 27 2014

Status

approved