A061370 a(n) = floor(ratio of product and sum of first n numbers).

1, 0, 1, 2, 8, 34, 180, 1120, 8064, 65978, 604800, 6141046, 68428800, 830269440, 10897286400, 153844043294, 2324754432000, 37440781904842, 640237370572800, 11585247657984000, 221172909834240000, 4442690623626907826

Offset

1,4

Links

Harry J. Smith, Table of n, a(n) for n = 1..100

Formula

a(n) = floor(2*(n-1)! / (n+1)).

Example

a(6) = floor(720/21) = 34.

Maple

a:=n->floor(mul(j, j=1..n)/sum(j, j=1..n)):seq(a(n), n=1..23); # Zerinvary Lajos, Dec 07 2008

Mathematica

Table[ Floor[2*(n - 1)!/(n + 1)], {n, 1, 24} ]

Prog

(PARI) a(n) = { 2*(n-1)! \ (n+1) } \\ Harry J. Smith, Jul 22 2009

Crossrefs

Sequence in context: A030871 A030960 A121894 * A126328 A268558 A191569

Adjacent sequences: A061367 A061368 A061369 * A061371 A061372 A061373

Keyword

nonn,easy

Author

Amarnath Murthy, May 02 2001

Extensions

More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001

Status

approved