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

Author

R. H. Hardin, Aug 09 2014

Keywords

• nonn

Comments

Column 7 of A245995

Examples

			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
		

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