A280389 Odd semiprimes that can be represented as 2p+3q, where p and q are primes.

15, 21, 25, 35, 39, 49, 55, 57, 65, 77, 85, 91, 93, 95, 115, 119, 121, 129, 133, 143, 145, 155, 161, 169, 183, 185, 187, 203, 205, 209, 215, 217, 219, 221, 235, 247, 253, 259, 265, 287, 289, 295, 299, 301, 305, 309, 319, 323, 327, 329, 335, 341, 355, 361, 365, 371, 377, 391, 395, 403

Offset: 1

Author

Randy L. Ekl, Jan 02 2017

Keywords

• nonn

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A046315 (odd semiprimes).

Cf. A280405 (odd semiprimes which can NOT be represented as 2p+3q, where p and q are prime).

Programs

Maple

N:= 10^3: # to get all terms <= N
Primes:= select(isprime, [2, seq(i, i=3..N/2, 2)]):
Cands:= select(t -> t::odd and t <= N, {seq(seq(2*p+3*q, p=Primes), q=Primes)}):
sort(convert(select(numtheory:-bigomega=2, Cands), list)); # Robert Israel, Jan 09 2017