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A120841
a(n) = the n-th positive integer which is coprime to the number of positive divisors of n.
1
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
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
KEYWORD
nonn
AUTHOR
Leroy Quet, Aug 18 2006
EXTENSIONS
Extended by Ray Chandler, Aug 22 2006
STATUS
approved