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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
OFFSET
1,1
LINKS
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
Sequence in context: A013932 A302550 A310117 * A351066 A310118 A010335
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Definition rephrased by R. J. Mathar, Jun 23 2009
STATUS
approved