A175648 Semiprimes m such that m+4 is also semiprime.

6, 10, 21, 22, 34, 35, 51, 58, 65, 82, 87, 91, 111, 115, 118, 119, 129, 141, 142, 155, 183, 201, 202, 205, 209, 213, 214, 215, 217, 249, 274, 287, 291, 295, 298, 299, 301, 305, 319, 323, 335, 358, 361, 377, 382, 391, 394, 403, 407, 411, 413, 447, 454, 469, 478

Offset: 1

Author

Juri-Stepan Gerasimov, Aug 02 2010

Keywords

• nonn
• easy

Links

• Zak Seidov, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A001358, A001359, A175612.

Programs

Maple

select(t -> numtheory:-bigomega(t)=2 and numtheory:-bigomega(t+4)=2, [$1..1000]); # Robert Israel, Feb 12 2015

Mathematica

Select[Range@ 480, And[PrimeOmega@ # == 2, PrimeOmega[# + 4] == 2] &] (* Michael De Vlieger, Dec 09 2015 *)

PARI

isok(n) = (bigomega(n) == 2) && (bigomega(n+4) == 2); \\ Michel Marcus, Feb 12 2015

Extensions

Corrected (309 removed) by R. J. Mathar, Aug 03 2010

Definition corrected by Zak Seidov, Feb 12 2015