A085572 Denominator of 2*Sum(C(n,w)/w,w=1..n/2-1)+C(n, n/2)/(n/2) if n is even otherwise of 2*Sum(C(n,w)/w,w=1..(n-1)/2).

1, 1, 1, 1, 3, 3, 6, 1, 5, 5, 30, 30, 210, 210, 420, 210, 630, 630, 315, 315, 3465, 3465, 13860, 2772, 36036, 12012, 12012, 1716, 8580, 8580, 17160, 8580, 145860, 204204, 612612, 612612, 11639628, 11639628, 29099070, 29099070, 29099070, 29099070, 1322685, 14549535

Offset: 2

Author

N. J. A. Sloane, Jul 07 2003

Keywords

• nonn
• frac

Examples

			2, 6, 11, 20, 101/3, 175/3, 593/6, 173, 1502/5, 2684/5, 28649/30, ...
		

Crossrefs

Cf. A085568-A086673.

Programs

Maple

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