OFFSET
1,1
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
A165557(n) = (a(n)^2-1)/4-a(n).
EXAMPLE
For p=7, (p^2-1)/4-p=5, which is prime. For p=11, (p^2-1)/4-p=19, which is prime. p=13: (p^2-1)/4-p=29.
MATHEMATICA
Select[Prime[Range[180]], PrimeQ[(#^2 - 1) / 4 - #]&] (* Vincenzo Librandi, Apr 10 2013 *)
PROG
(Magma) [p: p in PrimesInInterval(5, 1200) | IsPrime(((p^2-1) div 4) - p)]; // Vincenzo Librandi, Apr 10 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Sep 22 2009
EXTENSIONS
Extended by R. J. Mathar, Sep 26 2009
STATUS
approved