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

1,1

Links

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

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

Crossrefs

Cf. A046315 (odd semiprimes).

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

Sequence in context: A273061 A129926 A020204 * A057489 A070811 A211375

Adjacent sequences: A280386 A280387 A280388 * A280390 A280391 A280392

Keyword

nonn

Author

Randy L. Ekl, Jan 02 2017

Status

approved