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A247938 Sum of divisors of 2^prime(n)-1. 1
4, 8, 32, 128, 2160, 8192, 131072, 524288, 8567136, 539922240, 2147483648, 138055271872, 2199187780272, 8817412930560, 140828559963840, 9008745449302368, 576463955735383776, 2305843009213693952, 147573953351708377936, 2361193635521975063040 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

b-file computed with factorizations in Wagstaff link. a(167) corresponding to 2^991-1 is currently the first unknown term. - Jens Kruse Andersen, Sep 28 2014

LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..166

Sam Wagstaff, The Cunningham Project

FORMULA

a(n) = A000203(A001348(n)). - Michel Marcus, Sep 27 2014

MAPLE

with(numtheory): A247938:=n->sigma(2^ithprime(n)-1): seq(A247938(n), n=1..20); # Wesley Ivan Hurt, Sep 27 2014

MATHEMATICA

Table[DivisorSigma[1, 2^Prime[n]-1], {n, 30}]

PROG

(MAGMA) [SumOfDivisors(2^p-1): p in PrimesUpTo(100)];

(PARI) vector(50, n, sigma(2^prime(n)-1)) \\ Derek Orr, Sep 27 2014

CROSSREFS

Cf. A000203, A001348, A075708, A034785.

Sequence in context: A103970 A227295 A034785 * A072868 A075398 A098579

Adjacent sequences:  A247935 A247936 A247937 * A247939 A247940 A247941

KEYWORD

nonn

AUTHOR

Vincenzo Librandi, Sep 27 2014

STATUS

approved

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Last modified January 23 04:16 EST 2020. Contains 331168 sequences. (Running on oeis4.)