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URL: https://oeis.org/A046843

⇱ A046843 - OEIS

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A046843
Numbers k such that k*2^k - k - 1 is prime.
2
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
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
KEYWORD
nonn,more
AUTHOR
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