A215439 - OEIS

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A215439

Numbers k such that 2^k + k^2 - 1 is prime.

4

1, 2, 4, 10, 70, 134, 146, 190, 218, 292, 478, 7136, 15964, 19988, 100790, 111442, 181874, 202112

(list; graph; refs; listen; history; text; internal format)

OFFSET

1,2

COMMENTS

a(17) > 150000. - Giovanni Resta, Mar 19 2014

a(19) > 3*10^5. - Robert Price, Apr 30 2014

LINKS

Table of n, a(n) for n=1..18.

MATHEMATICA

Select[Range[0, 9000], PrimeQ[2^# + #^2 - 1] &]

PROG

(Magma) [n: n in [0..1000] | IsPrime(2^n+n^2-1)]

(PARI) is(n)=ispseudoprime(2^n+n^2-1) \\ Charles R Greathouse IV, May 22 2017

CROSSREFS

Sequence in context: A080090 A125263 A326949 * A120402 A182238 A110073

Adjacent sequences: A215436 A215437 A215438 * A215440 A215441 A215442

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Sep 03 2012

EXTENSIONS

a(13)-a(16) from Giovanni Resta, Mar 19 2014

a(17)-a(18) from Robert Price, Apr 30 2014

STATUS

approved