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A247787
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Sum of divisors of 2*prime(n)-1.
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2
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4, 6, 13, 14, 32, 31, 48, 38, 78, 80, 62, 74, 121, 108, 128, 192, 182, 133, 160, 192, 180, 158, 288, 240, 194, 272, 252, 288, 256, 403, 288, 390, 448, 278, 480, 352, 314, 434, 494, 576, 576, 381, 512, 576, 528, 398, 422, 540, 608, 458, 768, 702, 532, 672
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OFFSET
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1,1
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COMMENTS
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See A005382 (primes p such that sigma(2p-1) = 2p).
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LINKS
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FORMULA
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EXAMPLE
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For n = 3; prime(3) = 5, a(3) = sigma(2*5-1) = sigma(9) = 13.
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PROG
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(Magma) [SumOfDivisors(2*p-1): p in PrimesUpTo(2000)]
(PARI) vector(100, n, sigma(2*prime(n)-1)) \\ Derek Orr, Sep 25 2014
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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