|
Search: id:A009287
|
|
|
| A009287 |
|
a(1) = 3; thereafter a(n+1) = least k with a(n) divisors. |
|
+0
5
|
|
| 3, 4, 6, 12, 60, 5040, 293318625600, 670059168204585168371476438927421112933837297640990904154667968000000000000
(list; graph; listen)
|
|
|
OFFSET
|
1,1
|
|
|
COMMENT
|
The sequence must start with 3, since a(1)=1 or a(1)=2 would lead to a constant sequence. - M. F. Hasler, Sep 02 2008
Comment from Rick Shepherd, Aug 17, 2006: The calculation of a(7) and a(8) is based upon the method in A037019 (which, apparently, is the method previously used by the authors of A009287). So a(7) and a(8) are correct unless n=a(6)=5040 or n=a(7)=293318625600 are "exceptional" as described in A037019.
a(7) is correct because 5040 not exceptional (see A072066). [From T. D. Noe (noe(AT)sspectra.com), Sep 02 2008]
|
|
REFERENCES
|
Amarnath Murthy, Pouring a few more drops in the ocean of Smarandache Sequences and Conjectures (to be published in the Smarandache Notions Journal) [Note: this author submitted two erroneous versions of this sequence to the OEIS, A036480 and A061080, entries which contained invalid conjectures.]
|
|
LINKS
|
M. L. Perez et al., eds., Smarandache Notions Journal
|
|
FORMULA
|
a(n) = A005179(a(n-1)).
|
|
EXAMPLE
|
5040 is the smallest number with 60 divisors.
|
|
CROSSREFS
|
Cf. A000005, A005179, A037019.
Sequence in context: A160684 A137333 A006719 this_sequence A061080 A137027 A102733
Adjacent sequences: A009284 A009285 A009286 this_sequence A009288 A009289 A009290
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
David W. Wilson (davidwwilson(AT)comcast.net) and James Kilfiger (jamesk(AT)maths.warwick.ac.uk)
|
|
EXTENSIONS
|
Entry revised by N. J. A. Sloane (njas(AT)research.att.com), Aug 25 2006
|
|
|
Search completed in 0.002 seconds
|
