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A099439
Numbers k such that A000295(k) = 2^k-k-1 is prime.
5
4, 10, 14, 16, 26, 50, 56, 70, 116, 2072, 6250, 13670, 14216, 14626, 396128
OFFSET
1,1
COMMENTS
The next term is > 400000.
Equals A063791 + 1. - Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 03 2008
Some of the results were computed using the PrimeFormGW (PFGW) primality-testing program. - Hugo Pfoertner, Nov 14 2019
EXAMPLE
a(1) = 4 because 2^4 - 4 - 1 = 11 is prime.
CROSSREFS
Cf. A000295 (2^n-n-1), A099440 (primes in A000295), A099441 (2^n-n-1 is a semiprime), A099442 (semiprimes in A000295).
Sequence in context: A310361 A310362 A310363 * A310364 A310365 A310366
KEYWORD
nonn,more,hard
AUTHOR
Hugo Pfoertner, Oct 18 2004
EXTENSIONS
a(15) (a PRP) from Karsten Bonath, Jun 07 2018
STATUS
approved