OFFSET
1,1
MATHEMATICA
PrimeNext[n_]:=Module[{k}, k=n+1; While[ !PrimeQ[k], k++ ]; k]; PrimePrev[n_]:=Module[{k}, k=n-1; While[ !PrimeQ[k], k-- ]; k]; f[n_]:=PrimeQ[2*n+1]; lst={}; Do[p=Prime[n]; If[f[p], If[f[PrimePrev[p]]&&f[PrimeNext[p]], AppendTo[lst, p]]], {n, 9!}]; lst
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Joseph Stephan Orlovsky, Dec 04 2009
STATUS
approved