OFFSET
1,1
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
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 *)
PROG
(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.
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Dec 26 2002
STATUS
approved