A215440 Numbers k such that 3^k + k^3 - 1 is prime.

1, 3, 5, 9, 65, 71, 225, 269, 651, 843, 1971, 4851, 13667, 13961, 33309, 168111

Offset: 1

Author

Vincenzo Librandi, Sep 03 2012

Keywords

• nonn
• more

Comments

a(17) > 2*10^5. - Robert Price, Apr 15 2014

Crossrefs

Cf. A215435.

Programs

Magma

[k: k in [0..800] | IsPrime(3^k + k^3 - 1)];

Mathematica

Select[Range[0, 3000], PrimeQ[3^# + #^3 - 1] &]

PARI

is(n)=ispseudoprime(3^n+n^3-1) \\ Charles R Greathouse IV, Jun 13 2017

Extensions

a(12)-a(16) from Robert Price, Apr 15 2014