A154427 Primes p such that p^2 + (p+1)/2 is also prime.

3, 7, 11, 23, 31, 43, 59, 67, 71, 107, 127, 139, 151, 239, 251, 283, 359, 367, 379, 479, 491, 587, 599, 631, 647, 659, 787, 811, 863, 919, 983, 991, 1031, 1063, 1171, 1303, 1319, 1423, 1427, 1483, 1523, 1579, 1583, 1607, 1627, 1723, 1831, 1847, 1907, 1931, 1999

Offset

1,1

Comments

The associated primes of the quadratic form are in A164580.

Links

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Example

For p=7, p^2+(p+1)/2=53 is prime, which adds p=7 to the sequence.

Mathematica

Select[Prime[Range[500]], PrimeQ[#^2+(#+1)/2]&] (* Harvey P. Dale, Dec 19 2010 *)

Prog

(Magma) [p: p in PrimesInInterval(3, 2000) | IsPrime(p^2+(p+1) div 2)]; // Vincenzo Librandi, Oct 12 2012

Crossrefs

Cf. A164580.

Sequence in context: A097452 A086505 A239227 * A287459 A095102 A192614

Adjacent sequences: A154424 A154425 A154426 * A154428 A154429 A154430

Keyword

nonn,easy

Author

Vincenzo Librandi, Aug 17 2009

Extensions

Edited and extended by R. J. Mathar, Aug 26 2009

Status

approved