OFFSET
1,1
COMMENTS
Dickson's conjecture implies that this sequence is infinite. - Charles R Greathouse IV, Jul 31 2012
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
a(n)=(3*A158708(n+1)-1)/2 Zak Seidov, Jul 31 2012
EXAMPLE
7 is in the sequence because (2 * 7 + 1)/3 = 5, which is also prime.
19 is in the sequence because (2 * 19 + 1)/3 = 13, which is also prime.
MATHEMATICA
Select[Range[7, 2539, 2], PrimeQ[#] && PrimeQ[(2# + 1)/3]&] (* Zak Seidov, Jul 31 2012 *)
Select[Prime[Range[400]], PrimeQ[(2 # + 1) / 3]&] (* Vincenzo Librandi, Apr 14 2013 *)
PROG
(PARI) is(n)=n%3==1 && isprime((2*n+1)/3) && isprime(n) \\ Charles R Greathouse IV, Jul 31 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Roger L. Bagula, Mar 10 2005
EXTENSIONS
New name from Charles R Greathouse IV, Jul 31 2012
STATUS
approved