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A015761
Numbers k such that phi(k) | sigma_3(k).
11
1, 2, 3, 6, 12, 14, 15, 30, 35, 38, 42, 54, 56, 70, 78, 87, 95, 105, 114, 126, 135, 140, 147, 168, 174, 182, 190, 209, 210, 215, 216, 222, 248, 258, 264, 270, 285, 294, 297, 315, 357, 418, 420, 430, 455, 456, 540, 546, 551, 570, 594, 609, 616, 627
OFFSET
1,2
COMMENTS
sigma_3(k) is the sum of the cubes of the divisors of k (A001158).
LINKS
MATHEMATICA
Select[Range[630], Divisible[DivisorSigma[3, #], EulerPhi[#]] &] (* Amiram Eldar, Jun 23 2019 *)
PROG
(PARI) isok(k) = (sigma(k, 3) % eulerphi(k)) == 0; \\ Michel Marcus, Jun 23 2019
CROSSREFS
Sequence in context: A324243 A015774 A015767 * A015763 A015769 A015765
KEYWORD
nonn
STATUS
approved