A125216 Semiprimes s such that s-/+4 are primes.

9, 15, 33, 57, 93, 177, 237, 267, 393, 453, 573, 597, 687, 723, 933, 1167, 1227, 1293, 1527, 1563, 1623, 1983, 2157, 2217, 2463, 2913, 3327, 3453, 3543, 4353, 4647, 5007, 5277, 5403, 5847, 5853, 6033, 6117, 6207, 6267, 6333, 6393, 7023, 7233, 8013, 8097

Offset

1,1

Links

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

Mathematica

Reap[Do[p=Prime[i]; If[PrimeQ[p+8]&&Total[Last/@FactorInteger[p+4]]==2, Sow[p+4]], {i, 2*10^3}]][[2, 1]]
Select[Range[8100], PrimeOmega[#]==2&&AllTrue[#+{4, -4}, PrimeQ]&] (* The program uses the AllTrue function from Mathematica version 10 *) (* Harvey P. Dale, Oct 29 2017 *)

Crossrefs

Sequence in context: A155775 A228096 A111148 * A058505 A133763 A146475

Adjacent sequences: A125213 A125214 A125215 * A125217 A125218 A125219

Keyword

nonn

Author

Zak Seidov, Nov 24 2006

Status

approved