%I #15 Nov 10 2015 10:42:08

%S 1,3,4,15,24,58,168,234,324,375,3327,5788,8344,15039,59116,62620

%N n such that (1+2*7^n)/3 is prime.

%C The numbers corresponding to a(11)-a(16) are only (extra-strong BPSW) probable primes. - _Charles R Greathouse IV_, Nov 10 2015

%t Select[Range@ 2000, PrimeQ[(1 + 2 7^#)/3] &] (* _Michael De Vlieger_, Nov 06 2015 *)

%o (PARI) is(n)=ispseudoprime((1+2*7^n)/3) \\ _Charles R Greathouse IV_, Nov 06 2015

%K nonn

%O 1,2

%A _James R. Buddenhagen_, Oct 24 2015

%E a(11)-a(14) from _Charles R Greathouse IV_, Nov 06 2015

%E a(15)-a(16) from _Charles R Greathouse IV_, Nov 09 2015