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 A096819 Exponents k such that 2^k - 19 is prime. 12
 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 (list; graph; refs; listen; history; text; internal format)
 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 Table of n, a(n) for n=1..29. Henri & 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 Exponents for primes of 2^k-d form: 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), A096819 (d=19), A096820 (d=21). Cf. A096502. Sequence in context: A134643 A039001 A023741 * A032699 A073088 A054059 Adjacent sequences: A096816 A096817 A096818 * A096820 A096821 A096822 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

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Last modified May 30 02:25 EDT 2023. Contains 363044 sequences. (Running on oeis4.)