A046847 Numbers k such that k*2^k - (k-1) is prime.

1, 2, 4, 6, 30, 32, 42, 120, 210, 248, 284, 574, 600, 628, 1600, 2800, 3396, 8892, 9426, 14630, 15444, 37384, 51062, 76364, 129566

Offset: 1

Author

Felice Russo

Keywords

• nonn
• hard
• more

Comments

All terms > 1 are even. - Robert Israel, Sep 22 2014

Crossrefs

Cf. A046846.

Programs

Maple

select(t -> isprime(t*2^t - (t-1)), [$1..5000]); # Robert Israel, Sep 22 2014

PARI

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

Extensions

New name from Michel Marcus, Sep 22 2014

a(12)-a(17) from Robert Israel, Sep 22 2014

a(18)-a(23) from Michael S. Branicky, May 12 2023

a(24)-a(25) from Michael S. Branicky, Aug 18 2024