A257060 Number of length n 1..(6+1) arrays with every leading partial sum divisible by 2 or 3.

4, 18, 81, 364, 1636, 7353, 33048, 148534, 667585, 3000456, 13485528, 60610609, 272413948, 1224362538, 5502888657, 24732693652, 111160914460, 499611933801, 2245502257776, 10092393813166, 45360191702017, 203871056692176

Offset

1,1

Links

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

Formula

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

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

Example

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

Crossrefs

Column 6 of A257062.

Sequence in context: A282708 A252823 A264191 * A181610 A264927 A257059

Adjacent sequences: A257057 A257058 A257059 * A257061 A257062 A257063

Keyword

nonn

Author

R. H. Hardin, Apr 15 2015

Status

approved