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 A100357 Numbers k such that 2^k + k^2 + 1 is prime. 20
 0, 6, 12, 18, 162, 192, 216, 420, 1524, 5112, 7404, 24216, 25944, 101832, 346854 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS a(15) > 200000. - Giovanni Resta, Mar 23 2014 All terms are multiples of 6. Corresponding primes of the form 2^n+n^2+1 are in A035325. - Zak Seidov, Apr 05 2014 a(16) > 5*10^5. - Robert Price, Jun 15 2014 LINKS MATHEMATICA {ta={{0}}, tb={{0}}}; Do[g=n; s=2^n+n^2+1; If[PrimeQ[s], Print[n]; ta=Append[ta, n]; tb=Append[tb, s]], {n, 0, 10000, 6}]; {ta, tb, g} Select[Range[0, 10000, 6], PrimeQ[2^# + #^2 + 1] &] (* Vincenzo Librandi, Sep 03 2012 *) PROG (MAGMA) [n: n in [0..800] | IsPrime(2^n + n^2 + 1) ] // Vincenzo Librandi, Sep 03 2012 (PARI) is(n)=isprime(2^n+n^2+1) \\ Charles R Greathouse IV, Jul 01 2013 CROSSREFS Cf. A001580, A063997, A035325. Sequence in context: A205859 A288794 A177708 * A190265 A135358 A187391 Adjacent sequences:  A100354 A100355 A100356 * A100358 A100359 A100360 KEYWORD nonn AUTHOR Labos Elemer, Nov 19 2004 EXTENSIONS Added a(1) from Vincenzo Librandi, Sep 03 2012 a(12)-a(14) from Giovanni Resta, Mar 23 2014 Mathematica codes edited by Zak Seidov, Apr 05 2014 a(15) from Robert Price, Jun 15 2014 STATUS approved

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Last modified September 27 16:20 EDT 2020. Contains 337383 sequences. (Running on oeis4.)