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A061422
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Numbers k such that 2^(k-1) + k is prime.
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4
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OFFSET
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1,2
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COMMENTS
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No other terms below 300000. - Giovanni Resta, Nov 12 2012
a(8) > 500000. - Robert Price, May 24 2014
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REFERENCES
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J.-M. De Koninck, Ces nombres qui nous fascinent, Entry 237, p. 66, Ellipses, Paris 2008.
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LINKS
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Table of n, a(n) for n=1..7.
K. S. Brown, The Sum of the Prime Factors of N. MathPages.com
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PROG
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(PARI) is(n)=isprime(2^(n-1)+n) \\ Charles R Greathouse IV, May 22 2017
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CROSSREFS
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Cf. A061421.
Equals A100359(n) + 1.
Sequence in context: A349006 A349838 A179859 * A206333 A088097 A064774
Adjacent sequences: A061419 A061420 A061421 * A061423 A061424 A061425
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KEYWORD
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hard,nonn
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AUTHOR
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Jason Earls, May 02 2001
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EXTENSIONS
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H. Zeisel found the probable prime 1885. - Benoit Cloitre, Jun 03 2002
New term 51381 from Nuutti Kuosa (see MathPages link). - Max Alekseyev, Feb 08 2009
Deleted an incorrect conjecture. - N. J. A. Sloane, Dec 27 2009
a(7) from Giovanni Resta, Nov 12 2012
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STATUS
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approved
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