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A165354
Primes p such that p+(p^2-1)/8 is integer but not a prime number.
4
3, 5, 11, 13, 19, 29, 37, 43, 47, 53, 59, 61, 67, 83, 89, 97, 101, 107, 109, 131, 137, 139, 149, 157, 163, 167, 173, 179, 181, 193, 197, 199, 211, 223, 227, 229, 239, 241, 251, 263, 269, 271, 277, 283, 293, 307, 313, 317, 331, 347, 349, 353, 359, 373, 379, 389
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
FORMULA
A000040 \ {{2} U A165353}. - R. J. Mathar, Sep 21 2009
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
Sequence in context: A059639 A059263 A066652 * A059638 A059265 A059314
KEYWORD
nonn,easy
AUTHOR
Vincenzo Librandi, Sep 16 2009
EXTENSIONS
Entries checked - R. J. Mathar, Sep 21 2009
STATUS
approved