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A121920 a(n) = n-th integer from among those positive integers k where GCD(k,n) = prime power >1. a(1) = 1. 0
1, 4, 9, 8, 25, 10, 49, 16, 27, 18, 121, 22, 169, 26, 36, 32, 289, 34, 361, 38, 54, 42, 529, 46, 125, 50, 81, 54, 841, 63, 961, 64, 88, 66, 120, 70, 1369, 74, 105, 78, 1681, 87, 1849, 86, 111, 90, 2209, 94, 343, 98, 141, 102, 2809, 106, 210, 110, 159, 114, 3481, 125 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

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

EXAMPLE

2,4,5,6,8,12,14,15,16,18,22,... is the sequence of positive integers k where GCD(k, 10) = p^j, j = positive integer, p = prime. 18 is the 10th of these integers, so a(10) = 18.

MATHEMATICA

f[n_] := Block[{c = n, k = 0}, If[n == 1, 1, While[c > 0, k++; While[Length[FactorInteger[GCD[k, n]]] != 1, k++ ]; c--; ]; k]]; Table[f[n], {n, 65}] (*Chandler*)

CROSSREFS

Sequence in context: A077662 A063718 A063748 * A318279 A065642 A285109

Adjacent sequences:  A121917 A121918 A121919 * A121921 A121922 A121923

KEYWORD

nonn

AUTHOR

Leroy Quet, Sep 02 2006

EXTENSIONS

Extended by Ray Chandler, Sep 06 2006

STATUS

approved

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Last modified March 25 12:11 EDT 2019. Contains 321470 sequences. (Running on oeis4.)