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 A156986 a(n) = (n!!)!!. 1
 1, 1, 2, 3, 384, 2027025, 10409396852733332453861621760000 (list; graph; refs; listen; history; text; internal format)
 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: A065586 A110931 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

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Last modified May 22 17:42 EDT 2022. Contains 353957 sequences. (Running on oeis4.)