OFFSET
1,1
COMMENTS
The primes (p^2 + 4)/5 are 73, 193, 337, 1009, 1249, etc.
All terms == 1 or 9 (mod 10). - Robert Israel, Sep 16 2016
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
MAPLE
select(p -> isprime(p) and isprime((p^2+4)/5), [seq(seq(10*i+j, j=[1, 9]), i=0..1000)]); # Robert Israel, Sep 16 2016
MATHEMATICA
Select[Prime[Range[200]], PrimeQ[(#^2 + 4)/5] &] (* Vincenzo Librandi, Oct 15 2012 *)
PROG
(Magma) [p: p in PrimesInInterval(7, 2500) | IsPrime((p^2+4) div 5)]; // Vincenzo Librandi, Oct 15 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Jan 09 2009, Dec 13 2010
EXTENSIONS
Corrected and extended by Zak Seidov, Jan 13 2009
STATUS
approved