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A239874 Integers n such that 2n^2+1 and 2n^3+1 are prime. 5
1, 6, 9, 21, 27, 30, 72, 96, 99, 162, 186, 204, 237, 264, 297, 321, 357, 360, 375, 492, 537, 621, 759, 819, 834, 897, 936, 1065, 1242, 1326, 1329, 1359, 1419, 1494, 1506, 1596, 1662, 1704, 1740, 1749, 1761, 1842, 1869, 2157, 2175, 2250, 2274, 2451, 2547 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

All terms >1 are multiples of 3. Also, no term is congruent to 3 modulo 5.

LINKS

Zak Seidov, Table of n, a(n) for n = 1..1367 All terms up to 20000.

MATHEMATICA

s={1}; Do[If[PrimeQ [2k^2+1]&&PrimeQ[2k^3+1], AppendTo[s, k]], {k, 3, 10^3, 3}]; s

Select[Range[3500], PrimeQ[2 #^2 + 1] && PrimeQ[2 #^3 + 1]&] (* Vincenzo Librandi, Mar 29 2014 *)

PROG

(PARI) s=[]; for(n=1, 4000, if(isprime(2*n^2+1) && isprime(2*n^3+1), s=concat(s, n))); s \\ Colin Barker, Mar 28 2014

CROSSREFS

Intersection of A089001 and A168550.

Sequence in context: A154783 A096546 A165717 * A043103 A242756 A268665

Adjacent sequences:  A239871 A239872 A239873 * A239875 A239876 A239877

KEYWORD

nonn

AUTHOR

Zak Seidov, Mar 28 2014

STATUS

approved

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Last modified July 10 15:36 EDT 2020. Contains 335576 sequences. (Running on oeis4.)