|
| |
|
|
A107655
|
|
a(n) is the smallest number m greater than 1 such that phi(m)=d(m)^n, where d(m) is number of positive divisors of m; if there is no such m, a(n)=1.
|
|
1
| |
|
|
3, 5, 85, 17, 1285, 4369, 559876, 257, 327685, 1114129, 1114521441417, 16843009, 160490068541289, 1925878801139721, 23110536763219977, 65537, 3327917287071744009, 39934999967815157769, 479219999336720898057
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,1
|
|
|
COMMENTS
| For n=0,1,2,3 & 4 a(2^n)=F_n=A000215(n), where F_n is the n-th Fermat prime. Conjecture : a(11)=1.
Conjecture: A000005(a(n)) <= 12 for all n. [From Max Alekseyev (maxale(AT)gmail.com), May 07 2010]
|
|
|
EXAMPLE
| a(10)=1114129 because phi(1114129)=d(1114129)^10 and 1114129 is the smallest number m greater than 1 that phi(m)=d(m)^10.
|
|
|
CROSSREFS
| Cf. A000215, A033844.
Sequence in context: A122912 A062214 A144617 * A133660 A057663 A056244
Adjacent sequences: A107652 A107653 A107654 * A107656 A107657 A107658
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Farideh Firoozbakht (mymontain(AT)yahoo.com), Jun 06 2005
|
|
|
EXTENSIONS
| Terms a(11) onward from Max Alekseyev (maxale(AT)gmail.com), May 07 2010
|
| |
|
|
