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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: A084807 A184032 A361855 * 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 December 5 03:25 EST 2023. Contains 367567 sequences. (Running on oeis4.)