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A309607
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Exponents k for which reversal(2^k-1) is prime.
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0
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2, 3, 5, 53, 189, 293, 1107, 2181, 2695, 2871, 7667, 19999, 27471, 44537, 62323, 134367, 174295
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OFFSET
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1,1
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COMMENTS
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According to the statements in the first link given below, the terms for k <= 7667, the primes of the form reversal(2^k-1) are certified and for k >= 19999 they are probable primes.
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LINKS
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EXAMPLE
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5 is included because for n=5, reversal(2^5-1)=13 is prime.
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MATHEMATICA
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Select[Range[7667], PrimeQ[IntegerReverse[2^# - 1]] &]
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PROG
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(PARI) isok(k) = isprime(fromdigits(Vecrev(digits(2^k-1)))); \\ Michel Marcus, Aug 10 2019
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CROSSREFS
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KEYWORD
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nonn,base,more
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AUTHOR
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STATUS
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approved
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