A122042 Numbers k such that (2^k+k)/(k+2) is prime.

13, 19, 55, 469, 3385

Offset

1,1

Comments

All terms are also in A081765 = numbers k such that k+2 divides 2^(k-1) - 1.

Links

Table of n, a(n) for n=1..5.

Mathematica

Do[If[PrimeQ[(2^n+n)/(n+2)], Print[n]], {n, 1, 5000}]

Prog

(PARI) is(n)=ispseudoprime((2^n+n)/(n+2)) \\ Charles R Greathouse IV, Jun 13 2017

Crossrefs

Cf. A081765.

Sequence in context: A274424 A180528 A109504 * A291862 A217065 A339917

Adjacent sequences: A122039 A122040 A122041 * A122043 A122044 A122045

Keyword

nonn,more

Author

Zak Seidov, Sep 14 2006

Extensions

a(5) from Alexander Adamchuk, Sep 17 2006

Status

approved