A064040 Integers whose number of distinct prime divisors is prime.
6, 10, 12, 14, 15, 18, 20, 21, 22, 24, 26, 28, 30, 33, 34, 35, 36, 38, 39, 40, 42, 44, 45, 46, 48, 50, 51, 52, 54, 55, 56, 57, 58, 60, 62, 63, 65, 66, 68, 69, 70, 72, 74, 75, 76, 77, 78, 80, 82, 84, 85, 86, 87, 88, 90, 91, 92, 93, 94, 95, 96, 98, 99, 100, 102, 104, 105
Offset: 1
Examples
210 = 2*3*5*7 has 4 prime factors, hence it is not here, but it is part of A024619.
Links
- Harry J. Smith, Table of n, a(n) for n = 1..1000
Programs
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Maple
q:= n-> isprime(nops(ifactors(n)[2])): select(q, [$1..210])[]; # Alois P. Heinz, Apr 18 2024
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Mathematica
Select[Range[200], PrimeQ[PrimeNu[#]] &] (* Paolo Xausa, Mar 28 2024 *)
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PARI
n=0; for (m=1, 10^9, if (isprime(omega(m)), write("b064040.txt", n++, " ", m); if (n==1000, break))) \\ Harry J. Smith, Sep 06 2009 -
PARI
is(n)=isprime(omega(n)) \\ Charles R Greathouse IV, Sep 18 2015
Extensions
Edited by Charles R Greathouse IV, Mar 18 2010
Name edited by Michel Marcus, Oct 16 2023
Comments