A046847 - OEIS

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A046847

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

2

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

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OFFSET

1,2

COMMENTS

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

LINKS

Table of n, a(n) for n=1..25.

MAPLE

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

PROG

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

CROSSREFS

Sequence in context: A279419 A077633 A006933 * A339759 A121069 A100838

Adjacent sequences: A046844 A046845 A046846 * A046848 A046849 A046850

KEYWORD

nonn,hard,more

AUTHOR

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

STATUS

approved