OFFSET
1,1
COMMENTS
For p=2, p+(p^2-1)/8 is not integer; for all others, p=4k+-1, it is integer.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 1..1000
FORMULA
MATHEMATICA
Select[Prime[Range[2, 500]], ! PrimeQ[(#^2 - 1) / 8 + #]&] (* Vincenzo Librandi, Sep 12 2013 *)
PROG
(Magma) [p: p in PrimesUpTo(500)| not IsPrime(Floor(p+(p^2-1)/8))]; // Vincenzo Librandi, Sep 12 2013
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Sep 16 2009
EXTENSIONS
Entries checked - R. J. Mathar, Sep 21 2009
STATUS
approved