OFFSET
1,1
COMMENTS
n is a Sophie Germain prime and a twin prime, and 2*n+1 is also a twin prime.
Apparently this contains 3 and the members of A069142. - R. J. Mathar, Aug 23 2015
LINKS
Harvey P. Dale, Table of n, a(n) for n = 1..1000
FORMULA
a(n+1) = A069142(n), n>=1. - G. C. Greubel, Aug 23 2015
EXAMPLE
809 is a term because 809 and 811 are twin primes, and 2*809+1 = 1619 is a prime and a twin prime with 1621.
MATHEMATICA
sgtpQ[n_]:=Module[{sgp=2n+1}, PrimeQ[sgp]&&AnyTrue[sgp+{2, -2}, PrimeQ]]; Select[Union[Flatten[Select[Partition[Prime[Range[25000]], 2, 1], #[[2]]- #[[1]] ==2&]]], sgtpQ] (* The program uses the AnyTrue function from Mathematica version 10 *)
p=PrimeQ; Select[Prime@ Range[10^5], p[2#+1] && (p[#+2] || p[#-2]) && (p[2#+3] || p[2#-1]) &] (* Giovanni Resta, Aug 20 2015 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
Harvey P. Dale, Aug 20 2015
STATUS
approved