A113549 a(n) = product of n successive numbers up to n, if n is even a(n) = n*(n-1)*.. = n!, if n is odd a(n) = n(n+1)(n+2)... 'n' terms.

1, 2, 60, 24, 15120, 720, 8648640, 40320, 8821612800, 3628800, 14079294028800, 479001600, 32382376266240000, 87178291200, 101421602465863680000, 20922789888000, 415017197290314178560000, 6402373705728000, 2149789081963827444940800000

Offset: 1

Author

Amarnath Murthy, Nov 03 2005

Keywords

• easy
• nonn

Examples

			a(3) = 3*4*5 = 60.
a(4) = 4*3*2*1 = 24.
		

Links

• G. C. Greubel, Table of n, a(n) for n = 1..350

Crossrefs

Cf. A113550.

Programs

Mathematica

n = 1; anfunc[n_] := (If [OddQ[n], {an = n, Do[an = an*(n + i), {i, n - 1}]}, an = n! ]; an); Table[anfunc[n], {n, 1, 19}] (* Elizabeth A. Blickley (Elizabeth.Blickley(AT)gmail.com), Mar 10 2006 *)

Formula

a(1) = 1, a(2n) = (2n)!, a(2n-1) = (4n-3)!/(2n-2)!.

a(2n)*a(2n+1) = (4n+1)!.

Extensions

More terms from Elizabeth A. Blickley (Elizabeth.Blickley(AT)gmail.com), Mar 10 2006