login
A156986
a(n) = (n!!)!!.
1
1, 1, 2, 3, 384, 2027025, 10409396852733332453861621760000
OFFSET
0,3
LINKS
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
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