A245994 Number of length n+2 0..7 arrays with no pair in any consecutive three terms totalling exactly 7

344, 2120, 13064, 80504, 496088, 3057032, 18838280, 116086712, 715358552, 4408238024, 27164786696, 167396958200, 1031546535896, 6356676173576, 39171603577352, 241386297637688, 1487489389403480, 9166322634058568

Offset

1,1

Comments

Column 7 of A245995

Links

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

Formula

Empirical: a(n) = 6*a(n-1) +a(n-2).

Empirical: G.f.: -8*x*(43+7*x) / ( -1+6*x+x^2 ). - R. J. Mathar, Aug 10 2014

Example

Some solutions for n=4
..5....1....5....1....7....6....7....7....0....4....2....7....0....1....7....6
..6....0....3....3....6....6....4....1....6....1....6....5....2....3....6....5
..3....0....3....3....5....2....6....7....2....5....0....5....0....7....2....4
..7....4....5....3....4....2....4....5....4....3....6....1....1....7....7....1
..3....6....3....2....7....2....6....1....1....5....6....0....5....6....7....2
..7....5....6....3....1....7....6....3....0....6....6....0....7....5....7....2

Crossrefs

Sequence in context: A237243 A183680 A183674 * A246630 A250921 A262791

Adjacent sequences: A245991 A245992 A245993 * A245995 A245996 A245997

Keyword

nonn

Author

R. H. Hardin, Aug 09 2014

Status

approved