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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. 0
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 (list; graph; refs; listen; history; text; internal format)
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}] (*Chandler*)

CROSSREFS

Sequence in context: A319344 A260443 A206242 * A066838 A228151 A276087

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

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Last modified July 23 15:58 EDT 2019. Contains 325258 sequences. (Running on oeis4.)