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A247952
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Numbers k such that 2^k + 31 is prime.
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7
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4, 12, 36, 540, 844, 1192, 12136, 84280, 128356, 317464, 3018556
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OFFSET
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1,1
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COMMENTS
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Some terms correspond to probable primes. Lifchitz link shows Paul Underwood discovered 84280, and Lelio R Paula found 128356 and 317464 are in the sequence. - Jens Kruse Andersen, Sep 29 2014
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LINKS
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FORMULA
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MATHEMATICA
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Select[Range[0, 10000], PrimeQ[2^# + 31] &]
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PROG
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(Magma) [n: n in [0..2000]| IsPrime(2^n+31)];
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CROSSREFS
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Cf. Numbers k such that 2^k + d is prime: (0,1,2,4,8,16) for d=1; A057732 (d=3), A059242 (d=5), A057195 (d=7), A057196 (d=9), A102633 (d=11), A102634 (d=13), A057197 (d=15), A057200 (d=17), A057221 (d=19), A057201 (d=21), A057203 (d=23), A157006 (d=25), A157007 (d=27), A156982 (d=29), this sequence (d=31), A247953 (d=33), A220077 (d=35).
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(9)-a(10) (discovered by Lelio R Paula; see the Lifchitz link) added by Robert Price, Oct 04 2015
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STATUS
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approved
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