OFFSET
1,1
COMMENTS
b-file computed with factorizations in Wagstaff link. a(166) corresponding to 2^983+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..165
Sam Wagstaff, The Cunningham Project
FORMULA
MAPLE
with(numtheory): A247939:=n->sigma(2^ithprime(n)+1): seq(A247939(n), n=1..20); # Wesley Ivan Hurt, Sep 27 2014
MATHEMATICA
Table[DivisorSigma[1, 2^Prime[n] + 1], {n, 1, 20}]
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
KEYWORD
nonn
AUTHOR
Vincenzo Librandi, Sep 27 2014
STATUS
approved