A156986 a(n) = (n!!)!!.

1, 1, 2, 3, 384, 2027025, 10409396852733332453861621760000

Offset

0,3

Links

G. C. Greubel, Table of n, a(n) for n = 0..8

Formula

a(n) = A006882(A006882(n)). - R. J. Mathar, Feb 22 2009

Maple

doublefactorial(doublefactorial(n)) ; # R. J. Mathar, Feb 22 2009

Mathematica

Factorial2[Factorial2[Range[0, 10]]] (* G. C. Greubel, Jan 07 2022 *)

Prog

(Magma)
DoubleFactorial:=func< n | &*[n..2 by -2] >; // A006882
[DoubleFactorial(DoubleFactorial(n)): n in [0..9] ]; // G. C. Greubel, Jan 07 2022
(Sage) [(n.multifactorial(2)).multifactorial(2) for n in (0..9)] # G. C. Greubel, Jan 07 2022

Crossrefs

Cf. A006882.

Sequence in context: A110931 A355323 A097654 * A066849 A071219 A109855

Adjacent sequences: A156983 A156984 A156985 * A156987 A156988 A156989

Keyword

nonn

Author

Aart Blokhuis (aartb(AT)win.tue.nl), Feb 20 2009

Extensions

Another term with fewer than 80 digits added by R. J. Mathar, Feb 22 2009

a(0) prepended by G. C. Greubel, Jan 07 2022

Status

approved