A124201 a(n) = n-th positive integer from among those positive integers which are coprime to every noncomposite (1 or prime) which is < n and does not divide n.

1, 2, 5, 5, 13, 7, 23, 17, 27, 17, 43, 18, 59, 32, 43, 43, 79, 36, 97, 50, 71, 62, 113, 58, 125, 79, 109, 79, 157, 53, 173, 118, 131, 113, 167, 94, 211, 134, 167, 125, 239, 96, 257, 158, 191, 173, 281, 146, 283, 167, 237, 194, 331, 167, 295, 202, 267, 227, 373, 144

Offset

1,2

Comments

For which n's are n and a(n) coprime?

Links

Table of n, a(n) for n=1..60.

Example

The primes < 8 and coprime to 8 are 3, 5 and 7. The positive integers which are coprime to these primes (i.e. which are coprime to 3*5*7) are 1, 2, 4, 8, 11, 13, 16, 17, 19, ...a(8) is the 8th of these integers, which is 17.

Mathematica

f[n_] := Block[{c = n, k = 0, p}, p = Times @@ Select[Range[n - 1], PrimeQ[ # ] && GCD[ #, n] == 1 &]; While[c > 0, k++; While[GCD[k, p] > 1, k++ ]; c--; ]; k]; Table[f[n], {n, 61}] (* Ray Chandler, Dec 11 2006 *)

Crossrefs

Sequence in context: A138316 A183719 A239340 * A100953 A112835 A206625

Adjacent sequences: A124198 A124199 A124200 * A124202 A124203 A124204

Keyword

nonn

Author

Leroy Quet, Dec 07 2006

Extensions

Extended by Ray Chandler, Dec 11 2006

Status

approved