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A253851
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Mersenne primes (A000668) of the form 2^sigma(n) - 1 for some n.
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4
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OFFSET
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1,1
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COMMENTS
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Numbers n such that 2^sigma(n) - 1 is a Mersenne primes are given in A253849.
Sequence of corresponding values of sigma(n) are given in A253850 and each term of this sequence must be a prime from the sequence of Mersenne exponents (A000043).
If a(6) exists, it must be bigger than A000668(43) = 2^30402457-1.
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LINKS
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EXAMPLE
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Mersenne prime 2147483647 is in the sequence because there are two numbers n (16 and 25) with 2^sigma(n) - 1 = 2^31 - 1 = 2147483647.
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PROG
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(Magma) Set(Sort([(2^SumOfDivisors(n))-1: n in[1..10000] | IsPrime((2^SumOfDivisors(n))-1)]))
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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