A115585 Semiprimes with a semiprime sum of factors.

4, 9, 14, 21, 25, 26, 33, 38, 46, 49, 57, 62, 69, 74, 85, 93, 94, 106, 121, 129, 133, 134, 145, 166, 169, 177, 178, 205, 213, 217, 218, 226, 237, 249, 253, 254, 262, 265, 278, 289, 309, 314, 334, 361, 362, 393, 398, 417, 422, 445, 466, 469, 489, 493, 502, 505

Offset: 1

Author

Zak Seidov, Mar 09 2006

Keywords

• nonn

Examples

			314 = 2*157 and 2 + 157 = 159 =3 * 53 (semiprime).
		

Links

• Zak Seidov, Table of n, a(n) for n = 1..1000

Crossrefs

Cf. A001358, A068318.

Programs

Mathematica

fQ[n_] := Plus @@ Last /@ FactorInteger@n == 2; Select[ Range@513, fQ@# && fQ[ Plus @@ Flatten[ Table[First@#, {Last@#}] & /@ FactorInteger@# ]] &] (* Robert G. Wilson v *)
Select[Range[600],PrimeOmega[#]==PrimeOmega[Total[Flatten[Table[#[[1]],{#[[2]]}]&/@FactorInteger[#]]]]==2&] (* Harvey P. Dale, Jan 22 2013 *)

PARI

list(lim)=my(v=List()); forprime(p=2, sqrt(lim), forprime(q=p, lim\p, if(bigomega(p+q)==2, listput(v, p*q)))); vecsort(Vec(v)) \\ Charles R Greathouse IV, Sep 09 2012

Extensions

More terms from Robert G. Wilson v, Apr 12 2006