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Search: id:A124315
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A124315 a(n) = Sum_{ d divides n } sigma_0(lcm(d,n/d)), where sigma is the number of divisors function. +0
2
1, 2, 2, 4, 2, 4, 2, 6, 4, 4, 2, 8, 2, 4, 4, 9, 2, 8, 2, 8, 4, 4, 2, 12, 4, 4, 6, 8, 2, 8, 2, 12, 4, 4, 4, 16, 2, 4, 4, 12, 2, 8, 2, 8, 8, 4, 2, 18, 4, 8, 4, 8, 2, 12, 4, 12, 4, 4, 2, 16, 2, 4, 8, 16, 4, 8, 2, 8, 4, 8, 2, 24, 2, 4, 8, 8, 4, 8, 2, 18, 9, 4, 2, 16, 4, 4, 4, 12, 2, 16, 4, 8, 4, 4, 4, 24, 2, 8 (list; graph; listen)
OFFSET

1,2

FORMULA

a(p)=2 iff p is a prime.

MATHEMATICA

Table[Plus @@ Map[DivisorSigma[0, GCD[ #, n/# ]] &, Divisors@n], {n, 98}]

CROSSREFS

Cf. A001616, A061884, A124316.

Sequence in context: A118776 A092520 A129089 this_sequence A101113 A055155 A085191

Adjacent sequences: A124312 A124313 A124314 this_sequence A124316 A124317 A124318

KEYWORD

mult,nonn

AUTHOR

Robert G. Wilson v (rgwv(AT)rgwv.com), Sep 30 2006

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Last modified August 19 23:53 EDT 2008. Contains 142930 sequences.


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