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A015706 Odd numbers k that divide phi(k)*sigma(k). 2
1, 117, 135, 775, 819, 891, 1521, 1701, 2325, 3159, 3375, 4455, 5733, 6875, 6975, 10935, 11907, 19773, 20625, 20925, 22113, 22275, 24025, 40131, 41067, 43875, 44375, 49005, 61875, 62775, 68607, 72075, 75625, 83349, 84375, 85293 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
LINKS
Richard K. Guy, Divisors and desires, Amer. Math. Monthly, 104 (1997), 359-360.
MATHEMATICA
Select[Range[1, 85301, 2], Divisible[EulerPhi[#]DivisorSigma[1, #], #]&] (* Harvey P. Dale, Aug 27 2013 *)
PROG
(PARI) isok(n) = (n%2) && !(sigma(n)*eulerphi(n) % n); \\ Michel Marcus, Oct 02 2017
CROSSREFS
Cf. A011775.
Sequence in context: A176568 A023682 A084344 * A095625 A109023 A272388
KEYWORD
nonn
AUTHOR
STATUS
approved

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Last modified March 28 10:55 EDT 2024. Contains 371241 sequences. (Running on oeis4.)