A025535 a(n) = (1/C(2n,0) - 1/C(2n,1) + ... + d/C(2n,2n))*L, where d = (-1)^2n, L = LCM{C(2n,0), C(2n,1),..., C(2n,2n)}.

1, 3, 20, 105, 504, 4620, 51480, 45045, 1361360, 23279256, 21162960, 446185740, 2059318800, 5736673800, 155272637520, 4512611027925, 8494326640800, 8022419605200, 281206918792800, 267146572853160, 10431437606647200

Offset

0,2

Links

Table of n, a(n) for n=0..20.

Formula

a(n) = LCM{n+1, n+2, ..., 2*n+1}/(n+1). - Vladeta Jovovic, Oct 11 2002

Crossrefs

Sequence in context: A203357 A304494 A000917 * A119693 A158243 A139471

Adjacent sequences: A025532 A025533 A025534 * A025536 A025537 A025538

Keyword

nonn,easy

Author

Clark Kimberling

Extensions

More terms from James A. Sellers, May 05 2000

Status

approved