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A050934 Numbers n such that phi(n)*d(n) is a multiple of sigma(n), where d(n) is the number of divisors of n. 0
1, 3, 14, 35, 42, 105, 209, 248, 297, 418, 594, 627, 744, 1045, 1254, 1485, 1736, 2926, 3135, 3339, 3596, 3689, 3956, 4064, 4158, 5208, 5396, 5890, 6461, 7315, 7668, 8370, 8636, 8680, 8778, 8932, 9875, 10013, 10395, 10788, 11067, 11687 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Equality holds for 1, 3, 14, 42 and no others < 4290000000.

LINKS

Table of n, a(n) for n=1..42.

EXAMPLE

phi(35)*d(35)=4*24, a multiple of sigma(35)=48, so 35 is in the sequence.

MATHEMATICA

Select[Range[12000], Divisible[EulerPhi[#]DivisorSigma[0, #], DivisorSigma[ 1, #]]&] (* Harvey P. Dale, Jan 11 2019 *)

CROSSREFS

Cf. A000005, A000010, A000203.

Sequence in context: A076533 A081379 A081377 * A110427 A296294 A128916

Adjacent sequences:  A050931 A050932 A050933 * A050935 A050936 A050937

KEYWORD

nonn

AUTHOR

Jud McCranie, Dec 30 1999

STATUS

approved

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Last modified August 5 19:30 EDT 2020. Contains 336213 sequences. (Running on oeis4.)