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A047630 Numbers k that divide sigma(k) * phi(k) and are not divisible by 6. 0
1, 28, 40, 117, 135, 196, 200, 224, 496, 640, 775, 819, 891, 1000, 1372, 1521, 1550, 1568, 1701, 1792, 2176, 2325, 2480, 3100, 3159, 3200, 3375, 3724, 4455, 5000, 5632, 5733, 6200, 6860, 6875, 6975, 8128, 9604, 10240, 10880, 10935, 10976, 11907 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

REFERENCES

George E. Andrews, "Number Theory," Dover Books, NY, 1971, Page 84.

LINKS

Table of n, a(n) for n=1..43.

MATHEMATICA

Do[ If[ Mod[ n, 6 ]!=0, If[ Mod[ DivisorSigma[ 1, n ]*EulerPhi[ n ], n ]==0, Print[ n ] ] ], {n, 1, 25000} ]

CROSSREFS

Cf. A011775.

Sequence in context: A324858 A084807 A184032 * A135789 A219882 A154035

Adjacent sequences:  A047627 A047628 A047629 * A047631 A047632 A047633

KEYWORD

easy,nonn

AUTHOR

Robert G. Wilson v, Jul 22 2000

STATUS

approved

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Last modified July 4 04:47 EDT 2022. Contains 355064 sequences. (Running on oeis4.)