A120841 a(n) = the n-th positive integer which is coprime to the number of positive divisors of n.

1, 3, 5, 5, 9, 11, 13, 15, 13, 19, 21, 35, 25, 27, 29, 19, 33, 53, 37, 59, 41, 43, 45, 47, 37, 51, 53, 83, 57, 59, 61, 95, 65, 67, 69, 53, 73, 75, 77, 79, 81, 83, 85, 131, 133, 91, 93, 119, 73, 149, 101, 155, 105, 107, 109, 111, 113, 115, 117, 179, 121, 123, 187, 74, 129

Offset

1,2

Links

Table of n, a(n) for n=1..65.

Example

12 has 6 positive divisors. 1,5,7,11,13,17,19,23,25,29,31,35,37,...is the sequence of positive integers which are coprime to 6. 35 is the 12th of these integers, so a(12) = 35.

Mathematica

Table[Select[Range[300], CoprimeQ[#, DivisorSigma[0, n]]&][[n]], {n, 70}] (* Harvey P. Dale, Aug 29 2023 *)

Crossrefs

Cf. A000005.

Sequence in context: A090792 A076877 A332775 * A145282 A049757 A190864

Adjacent sequences: A120838 A120839 A120840 * A120842 A120843 A120844

Keyword

nonn

Author

Leroy Quet, Aug 18 2006

Extensions

Extended by Ray Chandler, Aug 22 2006

Status

approved