A085569 Denominator of 2*Sum(C(n,w)/(2*w+1),w=0..n/2-1)+C(n,n/2)/(n+1) if n is even, or of 2*Sum(C(n,w)/(2*w+1),w=0..(n-1)/2) if n is odd.

1, 1, 3, 1, 15, 3, 7, 15, 45, 5, 231, 21, 455, 315, 45, 3, 1683, 3465, 7315, 5005, 3003, 143, 13455, 585, 6825, 13923, 3213, 6545, 515185, 17765, 110143, 31977, 2078505, 62985, 1789515, 51129, 210197, 426075, 246675, 6325, 1400355, 34155, 41612175, 84192075

Offset

0,3

Links

Table of n, a(n) for n=0..43.

Example

1, 2, 8/3, 4, 88/15, 28/3, 104/7, 376/15, 1904/45, 372/5, 30152/231, ...

Maple

b := binomial; f1 := n->if n mod 2 = 0 then 2*add(b(n, w)/(2*w+1), w=0..n/2-1)+b(n, n/2)/(n+1); else 2*add(b(n, w)/(2*w+1), w=0..(n-1)/2); fi;

Crossrefs

Cf. A085568-A086673.

Sequence in context: A163239 A134145 A134146 * A336454 A261671 A198148

Adjacent sequences: A085566 A085567 A085568 * A085570 A085571 A085572

Keyword

nonn,frac

Author

N. J. A. Sloane, Jul 07 2003

Status

approved