A176140 Semiprimes s such that both s + 3 and s - 3 are primes.

10, 14, 26, 34, 86, 106, 134, 194, 226, 254, 274, 314, 334, 386, 446, 566, 974, 1094, 1126, 1226, 1234, 1286, 1294, 1486, 1546, 1874, 2066, 2374, 2386, 2554, 2854, 2906, 2966, 3086, 3166, 3254, 3326, 3466, 3694, 4054, 4286, 4594, 4786, 4874, 4934, 4954

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Apr 09 2010

Keywords

• nonn

Comments

2*5=10-+3->7,13 primes,...

Crossrefs

Cf. A125215, A125216

Programs

Mathematica

f[n_]:=Last/@FactorInteger[n]=={1,1};lst={};Do[If[f[n]&&PrimeQ[n-3]&&PrimeQ[n+3],AppendTo[lst,n]],{n,0,4*7!}];lst
Select[Range[5000],PrimeOmega[#]==2&&AllTrue[#+{3,-3},PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Nov 05 2017 *)

Extensions

Definition corrected by Zak Seidov, May 06 2013