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A174212 Ultradoublefactorials: a(n) = (n!!)^(n!!). 0
1, 1, 4, 27, 16777216, 437893890380859375, 500702078263459319174537025249570888246709955377400223021257741084821677152403456 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,3

COMMENTS

The next term (a(8)) has 993 digits. - Harvey P. Dale, Aug 17 2017

LINKS

Table of n, a(n) for n=0..6.

FORMULA

a(n) = A006882(n)^A006882(n).

EXAMPLE

For n=4 the doublefactorial is n!! = 4*2 = 8 and a(n) = n!!^n!! = 8^8 = 16777216.

MAPLE

P:=proc(i) local a, n; for n from 0 by 1 to i do print(doublefactorial(n)^doublefactorial(n)); od; end: P(10);

MATHEMATICA

udf[n_]:=Module[{c=n!!}, c^c]; Array[udf, 7, 0] (* Harvey P. Dale, Aug 17 2017 *)

CROSSREFS

Cf. A006882, A046882, A165812.

Sequence in context: A132640 A307031 A306823 * A038706 A222594 A153431

Adjacent sequences:  A174209 A174210 A174211 * A174213 A174214 A174215

KEYWORD

easy,nonn

AUTHOR

Paolo P. Lava & Giorgio Balzarotti, Mar 16 2010

STATUS

approved

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Last modified October 16 15:31 EDT 2019. Contains 328101 sequences. (Running on oeis4.)