A245993 Number of length n+2 0..6 arrays with no pair in any consecutive three terms totalling exactly 6.

216, 1116, 5766, 29790, 153906, 795144, 4108062, 21223992, 109652160, 566509902, 2926831878, 15121261374, 78122885724, 403616150730, 2085253182384, 10773307330236, 55659500700198, 287560720444278, 1485661331645130

Offset

1,1

Links

R. H. Hardin, Table of n, a(n) for n = 1..210

Formula

Empirical: a(n) = 4*a(n-1) + a(n-2) + 25*a(n-3) + 5*a(n-4).

Empirical g.f.: 6*x*(36 + 42*x + 181*x^2 + 35*x^3) / (1 - 4*x - x^2 - 25*x^3 - 5*x^4). - Colin Barker, Nov 06 2018

Example

Some solutions for n=5:
..2....3....0....4....0....0....2....0....4....2....0....0....0....4....2....2
..1....4....1....1....4....0....3....1....3....3....5....1....5....1....3....3
..3....6....2....4....1....2....2....0....5....2....4....1....4....6....6....6
..2....1....1....3....3....1....1....2....2....2....0....4....3....2....6....4
..1....6....1....5....0....0....3....1....0....3....5....4....4....5....3....3
..3....3....4....0....4....2....4....2....2....2....2....6....5....3....1....1
..4....1....4....2....1....3....1....6....2....6....0....3....4....2....6....0

Crossrefs

Column 6 of A245995.

Sequence in context: A162142 A233859 A233853 * A233980 A233974 A016863

Adjacent sequences: A245990 A245991 A245992 * A245994 A245995 A245996

Keyword

nonn

Author

R. H. Hardin, Aug 09 2014

Status

approved