A246478 Number of length n+3 0..7 arrays with no pair in any consecutive four terms totalling exactly 7.

1880, 10376, 57416, 317576, 1756472, 9714968, 53733080, 297195272, 1643773832, 9091640072, 50285457464, 278126631896, 1538306048600, 8508302434184, 47059042885064, 260281476168584, 1439605284832568, 7962392893359512

Offset

1,1

Links

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

Formula

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

Empirical g.f.: 8*x*(235 + 122*x + 222*x^2 + 43*x^3) / (1 - 5*x - 2*x^2 - 5*x^3 - x^4). - Colin Barker, Nov 06 2018

Example

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

Crossrefs

Column 7 of A246479.

Sequence in context: A235193 A072494 A260137 * A237103 A222799 A252111

Adjacent sequences: A246475 A246476 A246477 * A246479 A246480 A246481

Keyword

nonn

Author

R. H. Hardin, Aug 27 2014

Status

approved