A210544 Number of arrays of n nonnegative integers with value i>0 appearing only after i-1 has appeared at least 7 times.

1, 1, 1, 1, 1, 1, 1, 2, 4, 8, 16, 32, 64, 128, 257, 524, 1106, 2470, 5924, 15262, 41690, 118595, 345861, 1023028, 3050590, 9146312, 27567958, 83678750, 256632743, 798853376, 2537255097, 8264988956, 27723246374, 95941707086, 342355797248

Offset: 1

Author

R. H. Hardin, formula proved by R. J. Mathar in the Sequence Fans Mailing List, Mar 22 2012

Keywords

• nonn

Comments

Column 7 of A210545.

Examples

			Some solutions for n=19
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....0....0....0....0....0....0....0....0....0....0....0....0....0....0....0
..0....1....1....0....1....1....0....1....1....1....1....0....1....0....0....0
..1....1....0....0....0....1....1....0....0....1....1....1....0....1....1....1
..1....0....1....1....1....0....1....0....0....1....0....0....0....1....0....1
..0....1....0....0....0....1....1....0....1....1....1....1....0....1....1....1
..0....0....1....0....1....0....1....0....1....0....1....0....0....1....1....0
..1....0....0....1....1....1....0....0....0....1....1....0....1....1....1....0
..0....1....1....0....1....1....0....0....0....1....1....1....0....1....1....0
..0....1....1....0....1....1....0....0....1....0....1....0....0....1....1....1
..1....1....1....1....0....1....0....0....1....1....2....1....1....0....1....0
..1....1....1....1....0....2....0....0....0....1....1....1....1....0....2....1
..0....0....1....1....1....1....0....0....1....0....1....1....0....1....2....1
..0....1....1....1....0....2....1....1....1....0....0....0....1....1....2....1
		

Links

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

Crossrefs

Cf. A210545.

Formula

a(n) = 1 if n<=7 else Sum_{i=0..n-7} binomial(n-7,i)*a(i).