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A015766
Numbers n such that phi(n) | sigma_8(n).
9
1, 2, 3, 6, 19689, 39378
OFFSET
1,2
COMMENTS
sigma_8(n) is the sum of the 8th powers of the divisors of n.
sigma(16j+8,x)/phi(x) is integer for j = 0, ..., 500 and 6 actual terms of this sequence. Compare to A015759, A015762, A015770 and A091285. - Labos Elemer, May 27 2004
No additional terms up to 5 million. - Harvey P. Dale, Jan 31 2016
MATHEMATICA
Select[Range[40000], Divisible[DivisorSigma[8, #], EulerPhi[#]]&] (* Harvey P. Dale, Jan 31 2016 *)
CROSSREFS
KEYWORD
nonn
STATUS
approved