A100359 Numbers k such that 2^k + k + 1 is prime.

0, 2, 6, 236, 1884, 51380, 75764

Offset: 1

Author

Labos Elemer, Nov 19 2004

Keywords

• hard
• more
• nonn

Comments

a(8) > 500000. - Robert Price, May 24 2014

Crossrefs

Cf. A001580, A061422, A069539, A052007, A048744, A100357, A100358.

Programs

Mathematica

{ta={{0}}, tb={{0}}};Do[g=n;s=2^n+n+1; If[PrimeQ[s], Print[n];ta=Append[ta, n]; tb=Append[tb, s]], {n, 1, 10000}];{ta, tb, g}

PARI

is(n)=ispseudoprime(2^n+n+1) \\ Charles R Greathouse IV, Feb 20 2017

Formula

a(n) = A061422(n) - 1.

Extensions

a(6) from A061422 Max Alekseyev, Feb 08 2009

a(7) from Giovanni Resta, Mar 19 2014