A122212 a(n) is the n-th integer among the positive integers coprime to the sum of the divisors of n.

1, 2, 5, 4, 13, 17, 13, 14, 9, 29, 31, 27, 29, 41, 43, 16, 49, 29, 47, 67, 41, 65, 67, 89, 25, 89, 67, 65, 107, 89, 61, 55, 97, 101, 103, 45, 77, 139, 89, 149, 143, 125, 93, 151, 145, 137, 139, 99, 77, 77, 151, 121, 157, 199, 163, 209, 141, 217, 221, 209, 125, 185, 135

Offset

1,2

Links

Table of n, a(n) for n=1..63.

Example

8 = 1 + 7 is the sum of the divisors of 7. 1,3,5,7,9,11,13,15,17,19,21...are the positive integers which are coprime to 8. Of these integers, 13 is the 7th. So a(7) = 13.

Mathematica

f[n_] := Block[{c = n, k = 0}, While[c > 0, k++; While[GCD[DivisorSigma[1, n], k] > 1, k++ ]; c-- ]; k ]; Table[f[n], {n, 63}] (* Ray Chandler, Aug 29 2006 *)

Crossrefs

Cf. A000203, A122213.

Sequence in context: A338073 A080067 A117824 * A264071 A212188 A331213

Adjacent sequences: A122209 A122210 A122211 * A122213 A122214 A122215

Keyword

nonn

Author

Leroy Quet, Aug 26 2006

Extensions

Extended by Ray Chandler, Aug 29 2006

Status

approved