A085573 2*Sum(floor(C(n,w)/w),w=1..n/2-1)+floor(C(n,n/2)/(n/2)) if n is even, otherwise 2*Sum(floor(C(n,w)/w),w=1..(n-1)/2).

2, 6, 11, 20, 32, 56, 97, 172, 298, 534, 952, 1736, 3150, 5824, 10724, 20042, 37308, 70304, 131971, 250308, 473020, 901872, 1713596, 3281122, 6262254, 12033330, 23053047, 44431308, 85393280, 165008114, 318009610, 615878180, 1189803926, 2308781688

Offset

2,1

Links

Table of n, a(n) for n=2..35.

Maple

b := binomial; f3 := n->if n mod 2 = 0 then 2*add(floor(b(n, w)/w), w=1..n/2-1)+floor(b(n, n/2)/(n/2)); else 2*add(floor(b(n, w)/w), w=1..(n-1)/2); fi;

Crossrefs

Cf. A085568-A086672.

Sequence in context: A259411 A058760 A239071 * A171516 A081691 A085571

Adjacent sequences: A085570 A085571 A085572 * A085574 A085575 A085576

Keyword

nonn

Author

N. J. A. Sloane, Jul 07 2003

Status

approved