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A084679 Composite numbers with coprime numbers of prime factors with and without repetition. 2
12, 18, 20, 28, 44, 45, 48, 50, 52, 60, 63, 68, 72, 75, 76, 80, 84, 90, 92, 98, 99, 108, 112, 116, 117, 120, 124, 126, 132, 140, 147, 148, 150, 153, 156, 162, 164, 168, 171, 172, 175, 176, 180, 188, 192, 198, 200, 204, 207, 208, 212, 220, 228, 234, 236, 242 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

A001221(a(n))>1 and GreatestCommonDivisor(A001221(a(n)), A001222(a(n)))=1;

a(n)=A070011(n) for n<228, but A070011(228)=840=7*5*3*2^3 with omega=4 and bigOmega=6, as GCD(4,6)=2>1 840 is not a term.

LINKS

Charles R Greathouse IV, Table of n, a(n) for n = 1..10000

PROG

(PARI) is(n)=my(f=factor(n)[, 2]); #f>1 && gcd(vecsum(f), #f)==1 \\ Charles R Greathouse IV, Oct 19 2015

CROSSREFS

Different from A070011.

Sequence in context: A030515 A162947 A070011 * A072588 A267117 A187039

Adjacent sequences:  A084676 A084677 A084678 * A084680 A084681 A084682

KEYWORD

nonn

AUTHOR

Reinhard Zumkeller, Jun 28 2003

STATUS

approved

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Last modified July 5 08:02 EDT 2020. Contains 335464 sequences. (Running on oeis4.)