A046843 Numbers k such that k*2^k - k - 1 is prime.

2, 4, 8, 12, 16, 40, 80, 314, 478, 604, 634, 790, 868, 1264, 1376, 2536, 3544, 6564, 7268, 7780, 8366, 15010, 16636, 18672, 27084, 29954, 51968, 60940, 67044

Offset

1,1

Comments

The corresponding primes are given in A046842.

a(27) > 50000. - Tyler NeSmith, Apr 16 2022

a(30) > 10^5. - Michael S. Branicky, Sep 11 2024

Links

Table of n, a(n) for n=1..29.

Maple

A046843:=n->`if`(isprime(n*2^n-n-1), n, NULL): seq(A046843(n), n=1..1000); # Wesley Ivan Hurt, Oct 12 2014

Mathematica

Select[Range[10000], PrimeQ[# 2^#-#-1]&] (* Harvey P. Dale, Oct 10 2011 *)

Prog

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

Crossrefs

Cf. A046842.

Sequence in context: A371732 A368507 A273109 * A376256 A373728 A292060

Adjacent sequences: A046840 A046841 A046842 * A046844 A046845 A046846

Keyword

nonn,more

Author

Felice Russo

Extensions

Sign in definition corrected by R. J. Mathar, Oct 10 2010

a(10)-a(21) from Harvey P. Dale, Oct 10 2011

a(22)-a(26) from Tyler NeSmith, Apr 16 2022

a(27)-a(28) from Michael S. Branicky, May 17 2023

a(29) from Michael S. Branicky, Sep 11 2024

Status

approved