A084679 Composite numbers with coprime numbers of prime factors with and without repetition.

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

Offset: 1

Author

Reinhard Zumkeller, Jun 28 2003

Keywords

• nonn

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

Crossrefs

Different from A070011.

Programs

PARI

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