A165349 Primes p such that (p^2-1)/4-p is also prime.

7, 11, 13, 19, 23, 29, 41, 43, 59, 73, 79, 103, 109, 113, 131, 139, 173, 181, 191, 233, 263, 271, 283, 293, 311, 313, 331, 379, 389, 401, 409, 421, 433, 439, 443, 463, 491, 499, 521, 599, 613, 631, 641, 673, 701, 719, 751, 773, 839, 859, 929, 953, 983, 991, 1033, 1039, 1063

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

Cf. A165557.

Sequence in context: A115558 A067466 A091932 * A160024 A063911 A087489

Adjacent sequences: A165346 A165347 A165348 * A165350 A165351 A165352

Keyword

nonn,easy

Author

Vincenzo Librandi, Sep 22 2009

Extensions

Extended by R. J. Mathar, Sep 26 2009

Status

approved