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A161866
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Numbers k such that k^2+k+7 and k^2+k-7 are both prime.
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1
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3, 5, 9, 12, 24, 29, 32, 39, 44, 50, 57, 59, 65, 102, 135, 137, 144, 170, 180, 207, 260, 267, 297, 302, 305, 344, 347, 360, 365, 369, 389, 404, 429, 464, 474, 495, 540, 555, 570, 612, 620, 659, 662, 689, 767, 774, 792, 824, 837, 872, 885, 900, 950, 954, 989
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OFFSET
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1,1
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LINKS
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Daniel Starodubtsev, Table of n, a(n) for n = 1..10000
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EXAMPLE
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a(1)=3 as 12+-7 are primes. a(2)=5 as 30+-7 are primes.
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MATHEMATICA
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q=7; lst7={}; Do[p=n^2+n; If[PrimeQ[p-q]&&PrimeQ[p+q], AppendTo[lst7, n]], {n, 0, 7!}]; lst7
Select[Range[1000], AllTrue[#^2+#+{7, -7}, PrimeQ]&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Jun 26 2021 *)
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PROG
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(Magma) [k:k in [1..1000]| IsPrime(k^2+k+7) and IsPrime(k^2+k-7)]; // Marius A. Burtea, Feb 17 2020
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CROSSREFS
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Cf. A088485, A161863, A161864, A153417.
Sequence in context: A059093 A084593 A275843 * A102968 A180341 A348746
Adjacent sequences: A161863 A161864 A161865 * A161867 A161868 A161869
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KEYWORD
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nonn,easy
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AUTHOR
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Vladimir Joseph Stephan Orlovsky, Jun 20 2009
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EXTENSIONS
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Definition rephrased by R. J. Mathar, Jun 23 2009
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STATUS
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approved
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