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A161864 Numbers n such that n^2 + n + 5 and n^2 + n - 5 are both prime. 2
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

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

EXAMPLE

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

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

CROSSREFS

Cf. A088485, A161863.

Sequence in context: A013932 A302550 A310117 * A310118 A010335 A310119

Adjacent sequences:  A161861 A161862 A161863 * A161865 A161866 A161867

KEYWORD

nonn,easy

AUTHOR

Vladimir Joseph Stephan Orlovsky, Jun 20 2009

EXTENSIONS

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

STATUS

approved

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Last modified May 22 14:32 EDT 2019. Contains 323480 sequences. (Running on oeis4.)