A124655 a(n) = n-th integer from among those positive integers k where every positive integers <= k and coprime to k is also coprime to n.

1, 2, 3, 6, 5, 24, 7, 14, 21, 70, 11, 60, 13, 140, 180, 30, 17, 96, 19, 170, 357, 352, 23, 132, 105, 494, 75, 336, 29, 840, 31, 62, 924, 850, 1050, 204, 37, 1064, 1287, 370, 41, 1638, 43, 836, 630, 1564, 47, 276, 301, 470, 2244, 1170, 53, 312, 2695, 728, 2793

Offset

1,2

Links

Table of n, a(n) for n=1..57.

Example

The positive integers k, where every positive integer <= k and coprime to k is also coprime to 6, form the sequence 1,2,6,12,18,24,30,... So a(6) is the 6th of these integers, which is 24. (3, for example, is not among the sequence of k's because 2 is coprime to 3 and is <= 3, but 2 is not coprime to 6.)

Mathematica

f[n_] := Select[Range[n], GCD[ #, n] == 1 &]; g[n_] := Block[{k = 0, c = n}, While[c > 0, k++; While[Times @@ GCD[f[k], n] > 1, k++ ]; c--; ]; k]; Table[g[n], {n, 60}] (* Ray Chandler, Dec 24 2006 *)

Crossrefs

Sequence in context: A328316 A206242 A327454 * A338219 A066838 A228151

Adjacent sequences: A124652 A124653 A124654 * A124656 A124657 A124658

Keyword

nonn

Author

Leroy Quet, Dec 22 2006

Extensions

Extended by Ray Chandler, Dec 24 2006

Status

approved