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A165349 Primes p such that (p^2-1)/4-p is also prime. 2
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified October 23 23:51 EDT 2019. Contains 328379 sequences. (Running on oeis4.)