|
| |
|
|
A141114
|
|
Those positive integers n where d(d(n)) is coprime to n, where d(n) is the number of divisors of n.
|
|
2
| |
|
|
1, 3, 5, 7, 8, 9, 10, 11, 13, 14, 17, 19, 22, 23, 25, 26, 29, 31, 34, 35, 37, 38, 41, 43, 45, 46, 47, 49, 53, 55, 58, 59, 61, 62, 63, 65, 67, 71, 73, 74, 75, 77, 79, 81, 82, 83, 85, 86, 89, 91, 94, 95, 97, 99, 100, 101, 103, 105, 106, 107, 109, 113, 115, 117, 118, 119, 121
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 1,2
|
|
|
EXAMPLE
| 26 has 4 divisors and 4 has 3 divisors. 3 is coprime to 26, so 26 is in the sequence.
|
|
|
MATHEMATICA
| Select[Range[200], GCD[DivisorSigma[0, DivisorSigma[0, # ]], # ] == 1 &] - Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 05 2008
|
|
|
CROSSREFS
| Cf. A010553, A141113, A141115.
Sequence in context: A100318 A167707 A131903 * A136443 A020491 A168501
Adjacent sequences: A141111 A141112 A141113 * A141115 A141116 A141117
|
|
|
KEYWORD
| nonn
|
|
|
AUTHOR
| Leroy Quet Jun 04 2008
|
|
|
EXTENSIONS
| More terms from Stefan Steinerberger (stefan.steinerberger(AT)gmail.com), Jun 05 2008
|
| |
|
|
