A107707 3-almost primes whose prime factors sum to a prime.

12, 28, 45, 52, 63, 75, 76, 99, 117, 147, 148, 153, 165, 172, 175, 207, 245, 268, 273, 279, 316, 325, 333, 345, 369, 385, 388, 399, 412, 423, 435, 436, 475, 477, 507, 508, 549, 561, 595, 603, 651, 652, 657, 665, 715, 747, 759, 772, 775, 777, 795, 833, 845

Offset: 1

Author

Giovanni Teofilatto, Jun 10 2005

Keywords

• easy
• nonn

Examples

			a(5) = 63 = 3*3*7 because 3+3+7 = 13 is prime.
		

Links

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

Programs

Mathematica

Select[Range[1000],PrimeOmega[#]==3&&PrimeQ[Total[ Times@@@ FactorInteger[ #]]]&] (* Harvey P. Dale, Nov 10 2011 *)

PARI

list(lim)=my(v=List()); forprime(p=2,lim\4, forprime(q=2,min(p,lim\p\2), forprime(r=2,min(q,lim\p\q), if(isprime(p+q+r), listput(v,p*q*r))))); Set(v) \\ Charles R Greathouse IV, Feb 01 2017

Extensions

Corrected and extended by Ray Chandler, Jun 12 2005