A248432 Number of length n+2 0..7 arrays with every three consecutive terms having the sum of some two elements equal to twice the third.

80, 140, 252, 462, 884, 1684, 3200, 6216, 11944, 22810, 44396, 85402, 163204, 317716, 611248, 1168198, 2274196, 4375320, 8362052, 16278784, 31318664, 59855842, 116523764, 224179214, 428448488, 834077068, 1604674164, 3066832822

Offset

1,1

Links

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

Formula

Empirical: a(n) = a(n-1) + 10*a(n-3) - 10*a(n-4) - 22*a(n-6) + 22*a(n-7) + 12*a(n-9) - 12*a(n-10) - a(n-12) + a(n-13).

Empirical g.f.: 2*x*(40 + 30*x + 56*x^2 - 295*x^3 - 89*x^4 - 160*x^5 + 588*x^6 + 58*x^7 + 96*x^8 - 317*x^9 - 5*x^10 - 9*x^11 + 27*x^12) / ((1 - x)*(1 - 10*x^3 + 22*x^6 - 12*x^9 + x^12)). - Colin Barker, Nov 08 2018

Example

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

Crossrefs

Column 7 of A248433.

Sequence in context: A204648 A202447 A202440 * A107931 A234134 A134769

Adjacent sequences: A248429 A248430 A248431 * A248433 A248434 A248435

Keyword

nonn

Author

R. H. Hardin, Oct 06 2014

Status

approved