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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

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OFFSET

1,2

COMMENTS

a(2n)*a(2n+1) = (4n+1)!. a(2)*a(3) = 5!, a(4)*a(5) = 9!.

LINKS

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

FORMULA

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

EXAMPLE

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

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, 30}] - Elizabeth A. Blickley (Elizabeth.Blickley(AT)gmail.com), Mar 10 2006

CROSSREFS

Cf. A113550.

Sequence in context: A096758 A262638 A202622 * A268432 A117482 A078511

Adjacent sequences: A113546 A113547 A113548 * A113550 A113551 A113552

KEYWORD

easy,nonn

AUTHOR

Amarnath Murthy, Nov 03 2005

EXTENSIONS

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

STATUS

approved