A015706 - OEIS

A015706

Odd numbers k that divide phi(k)*sigma(k).

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

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OFFSET

1,2

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..3000

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

Adjacent sequences: A015703 A015704 A015705 * A015707 A015708 A015709

KEYWORD

nonn

AUTHOR

Robert G. Wilson v

STATUS

approved