login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Table of n, a(n) for n=1..15.

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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

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