A171161 Sophie Germain primes p surrounded by Sophie Germain primes.

2, 3, 20759, 103619, 145109, 148853, 199109, 291503, 353459, 356591, 362759, 367733, 475523, 521831, 527123, 552059, 603191, 609809, 639839, 691979, 726419, 810809, 812939, 825491, 940421, 980471, 998213, 1103561, 1117793, 1132811

Offset

1,1

Links

Table of n, a(n) for n=1..30.

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

Cf. A005384

Sequence in context: A115640 A212494 A197635 * A101445 A128668 A216977

Adjacent sequences: A171158 A171159 A171160 * A171162 A171163 A171164

Keyword

nonn

Author

Vladimir Joseph Stephan Orlovsky, Dec 04 2009

Status

approved