A161864 Numbers n such that n^2 + n + 5 and n^2 + n - 5 are both prime.

3, 6, 11, 18, 21, 23, 27, 32, 42, 48, 51, 83, 86, 93, 116, 153, 158, 182, 188, 216, 282, 291, 317, 333, 396, 482, 681, 737, 786, 798, 818, 821, 872, 923, 956, 966, 977, 986, 1007, 1026, 1077, 1082, 1106, 1161, 1287, 1292, 1302, 1337, 1341, 1451, 1467, 1563

Offset: 1

Author

Vladimir Joseph Stephan Orlovsky, Jun 20 2009

Keywords

• nonn
• easy

Examples

			a(1)=3 as 12+-5 are primes. a(2)=6 as 42+-5 are primes.
		

Links

• Robert Israel, Table of n, a(n) for n = 1..10000

Crossrefs

Cf. A088485, A161863.

Programs

Maple

select(n -> isprime(n^2+n+5) and isprime(n^2+n-5), [$1..2000]); # Robert Israel, Nov 26 2017

Mathematica

q=5;lst5={};Do[p=n^2+n;If[PrimeQ[p-q]&&PrimeQ[p+q],AppendTo[lst5,n]], {n,0,7!}];lst5

Extensions

Definition rephrased by R. J. Mathar, Jun 23 2009