A120837 a(n) = the smallest positive integer which does not occur earlier in the sequence and which is coprime to the number of positive divisors of n.

1, 3, 5, 2, 7, 9, 11, 13, 4, 15, 17, 19, 21, 23, 25, 6, 27, 29, 31, 35, 33, 37, 39, 41, 8, 43, 45, 47, 49, 51, 53, 55, 57, 59, 61, 10, 63, 65, 67, 69, 71, 73, 75, 77, 79, 81, 83, 87, 14, 85, 89, 91, 93, 95, 97, 99, 101, 103, 105, 107, 109, 111, 113, 12, 115, 117, 119, 121

Offset

1,2

Comments

Sequence is a permutation of the positive integers.

Links

Table of n, a(n) for n=1..68.

Example

6 has 4 positive divisors. Among those positive integers not occurring among the first 5 terms of the sequence, 9 is the smallest which is coprime to 4. So a(6) = 9. 4, 6 and 8 also do not occur among the first 5 terms of the sequence, but they are not coprime to 4.

Crossrefs

Cf. A000005.

Sequence in context: A243352 A026184 A026208 * A208754 A180077 A095749

Adjacent sequences: A120834 A120835 A120836 * A120838 A120839 A120840

Keyword

nonn

Author

Leroy Quet, Aug 18 2006

Extensions

Extended by Ray Chandler, Aug 22 2006

Status

approved