A257061 Number of length n 1..(7+1) arrays with every leading partial sum divisible by 2 or 3.

5, 27, 141, 738, 3866, 20249, 106056, 555483, 2909419, 15238479, 79813616, 418034724, 2189514005, 11467878868, 60064583029, 314596463387, 1647741976789, 8630273820766, 45202238742834, 236752903766237, 1240025693431636

Offset

1,1

Links

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

Formula

Empirical: a(n) = 4*a(n-1) + 5*a(n-2) + 7*a(n-3) + 4*a(n-4).

Empirical g.f.: x*(5 + 7*x + 8*x^2 + 4*x^3) / (1 - 4*x - 5*x^2 - 7*x^3 - 4*x^4). - Colin Barker, Dec 20 2018

Example

Some solutions for n=4:
..4....6....4....8....3....6....6....6....2....2....2....3....4....4....3....3
..8....8....6....8....5....2....8....3....2....1....7....3....8....2....7....5
..4....1....5....6....8....4....2....1....4....7....6....8....6....6....5....8
..6....1....7....5....2....3....4....4....6....4....1....1....3....3....1....4

Crossrefs

Column 7 of A257062.

Sequence in context: A084177 A037675 A221673 * A052225 A293295 A343208

Adjacent sequences: A257058 A257059 A257060 * A257062 A257063 A257064

Keyword

nonn

Author

R. H. Hardin, Apr 15 2015

Status

approved