The OEIS mourns the passing of Jim Simons and is grateful to the Simons Foundation for its support of research in many branches of science, including the OEIS.
The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 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). Sum_{n>=1} 1/a(n) = A134877. - Amiram Eldar, Nov 11 2020 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, A134877, A165812. Sequence in context: A132640 A307031 A306823 * A352838 A038706 A358863 Adjacent sequences: A174209 A174210 A174211 * A174213 A174214 A174215 KEYWORD easy,nonn AUTHOR Paolo P. Lava & Giorgio Balzarotti, Mar 16 2010 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified May 23 16:36 EDT 2024. Contains 372765 sequences. (Running on oeis4.)