A174361 Primes p such that 2*p^2-+21 are also prime.

5, 13, 17, 19, 43, 71, 83, 97, 373, 383, 443, 541, 617, 787, 883, 1171, 1279, 1301, 1663, 1733, 1801, 1867, 1873, 2027, 2087, 2609, 2617, 2657, 2671, 2729, 2791, 2803, 2861, 2971, 3061, 3251, 3361, 3691, 3803, 3847, 4013, 4421, 4603, 4621, 4931, 5087

Offset

1,1

Links

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

Example

For p=5, 2*5^2-+21=(29,71); p=13, 2*13^2-+21=(317,359).

Mathematica

Select[Prime[Range[2, 1000]], PrimeQ[2 #^2 - 21]&&PrimeQ[2 #^2 + 21]&] (* Vincenzo Librandi, Apr 10 2013 *)

Prog

(Magma) [p: p in PrimesInInterval(3, 5100)|IsPrime(2*p^2-21) and IsPrime(2*p^2+21)];

Crossrefs

Sequence in context: A103666 A082700 A212287 * A226165 A166409 A077425

Adjacent sequences: A174358 A174359 A174360 * A174362 A174363 A174364

Keyword

nonn,easy

Author

Vincenzo Librandi, Mar 17 2010

Status

approved