A079141 Primes of the form p^2 + 6 where p is prime.

31, 127, 367, 967, 3727, 6247, 7927, 11887, 17167, 22807, 39607, 72367, 109567, 160807, 185767, 323767, 502687, 737887, 863047, 885487, 942847, 982087, 1079527, 1560007, 1739767, 1852327, 1985287, 2105407, 2343967, 2399407

Offset: 1

Author

Cino Hilliard, Dec 26 2002

Keywords

• easy
• nonn

Comments

Sum of reciprocals = 0.0447155381... [4 additional digits from Jon E. Schoenfield, Jan 15 2015]

Links

• T. D. Noe, Table of n, a(n) for n=1..1000

Crossrefs

Cf. A056909.

Programs

Mathematica

f[n_]:=n^2+6; lst={};Do[p=Prime[n];If[PrimeQ[f[p]],AppendTo[lst,f[p]]],{n,7!}];lst (* Vladimir Joseph Stephan Orlovsky, Jul 17 2009 *)
Select[#^2+6&/@Prime[Range[300]],PrimeQ] (* Harvey P. Dale, Nov 16 2012 *)

PARI

sqppn(n) = {sr=0; forprime(x=3,n, y = x*x+6; if(isprime(y), print1(y" "); sr+=1.0/y; ); ); print(); print(sr); } \\ Primes of the form p^2 + 6 and the sum of the reciprocals.