A245867 Number of length n+2 0..6 arrays with some pair in every consecutive three terms totalling exactly 6.

127, 493, 1579, 5515, 18505, 63241, 214315, 729097, 2475985, 8415217, 28590415, 97151683, 330100459, 1121650903, 3811203385, 12950003383, 44002376953, 149514426895, 508030458319, 1726221621517, 5865476355769, 19930126601527

Offset

1,1

Links

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

Formula

Empirical: a(n) = 3*a(n-1) + 3*a(n-2) - a(n-3) - 9*a(n-4) - 24*a(n-5) + 5*a(n-6).

Empirical g.f.: x*(127 + 112*x - 281*x^2 - 574*x^3 - 1141*x^4 + 245*x^5) / (1 - 3*x - 3*x^2 + x^3 + 9*x^4 + 24*x^5 - 5*x^6). - Colin Barker, Nov 04 2018

Example

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

Crossrefs

Column 6 of A245869.

Sequence in context: A057814 A038646 A340537 * A096523 A299132 A142736

Adjacent sequences: A245864 A245865 A245866 * A245868 A245869 A245870

Keyword

nonn

Author

R. H. Hardin, Aug 04 2014

Status

approved