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A247954
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a(n) = sigma(sigma(2n-1)).
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8
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1, 7, 12, 15, 14, 28, 24, 60, 39, 42, 63, 60, 32, 90, 72, 63, 124, 124, 60, 120, 96, 84, 168, 124, 80, 195, 120, 195, 186, 168, 96, 210, 224, 126, 252, 195, 114, 224, 252, 186, 133, 224, 280, 360, 234, 248, 255, 360, 171, 392, 216, 210, 508, 280, 216, 300
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OFFSET
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1,2
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COMMENTS
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See A247821 - numbers n such that sigma(sigma(2n-1)) is a prime p.
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LINKS
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FORMULA
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EXAMPLE
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For n=2; a(2) = sigma(sigma(2*2-1)) = sigma(sigma(3)) = sigma(4) = 7.
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MAPLE
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MATHEMATICA
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Table[DivisorSigma[1, DivisorSigma[1, 2 n - 1]], {n, 50}] (* Wesley Ivan Hurt, Oct 01 2014 *)
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PROG
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(Magma) [SumOfDivisors(SumOfDivisors(2*n-1)): n in [1..1000]]
(PARI) vector(100, n, sigma(sigma(2*n-1))) \\ Derek Orr, Sep 29 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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