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

1,1

Comments

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

Links

Table of n, a(n) for n=1..46.

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 *)

Crossrefs

Cf. A125215, A125216

Sequence in context: A175664 A053690 A177948 * A031028 A176810 A115603

Adjacent sequences: A176137 A176138 A176139 * A176141 A176142 A176143

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Apr 09 2010

Extensions

Definition corrected by Zak Seidov, May 06 2013

Status

approved