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A096819
Numbers k such that 2^k - 19 is prime.
13
5, 7, 11, 15, 19, 21, 31, 39, 67, 69, 85, 157, 171, 191, 255, 291, 379, 3669, 4551, 9531, 13119, 14211, 20647, 233965, 337267, 534429, 535415, 816039, 991715
OFFSET
1,1
COMMENTS
All terms are odd since for even k, 2^k - 19 is divisible by 3.
a(26) > 5*10^5. - Tyler NeSmith, Apr 16 2022
LINKS
Henri Lifchitz and Renaud Lifchitz, Search for 2^n-19, PRP Top Records.
EXAMPLE
2^7 - 19 = 128 - 19 = 109, a prime, so 7 is a term of the sequence.
MATHEMATICA
Select[Range[5, 20000], PrimeQ[2^#-19]&] (* Vladimir Joseph Stephan Orlovsky, Feb 27 2011*)
CROSSREFS
Cf. A096502.
Cf. Sequences of numbers k such that 2^k - d is prime: A000043 (d=1), A050414 (d=3), A059608 (d=5), A059609 (d=7), A059610 (d=9), A096817 (d=11), A096818 (d=13), A059612 (d=15), A059611 (d=17), this sequence (d=19), A096820 (d=21), A057220 (d=23), A356826 (d=29).
Sequence in context: A134643 A039001 A023741 * A032699 A073088 A054059
KEYWORD
nonn,more
AUTHOR
Labos Elemer, Jul 13 2004
EXTENSIONS
a(22)-a(23) from Max Alekseyev, Feb 10 2012
a(24)-a(25) from Lelio R Paula, added by Max Alekseyev, Oct 24 2013
a(26)-a(29) found by Stefano Morozzi, added by Alois P. Heinz, Aug 29 2022
STATUS
approved