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A078543 Balanced refactorable numbers. 2
1, 2, 12, 56, 248, 12192, 28896, 60960, 61344, 66528, 86304, 94944, 129504, 133920, 140448, 182880, 201924, 207264, 242316, 282720, 408672, 416640, 426720, 429408, 604128, 664608, 671760, 776736, 792480, 854496, 862752, 906528 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Donovan Johnson, Table of n, a(n) for n = 1..500

FORMULA

Intersection of A033950 and A020492.

EXAMPLE

n=56: tau(56)=8, sigma(56)=120, phi(56)=24, q1=120/24=5 for balancedness, q2=56/8=7 for refactorability

MATHEMATICA

Do[s=DivisorSigma[1, n]/EulerPhi[n]; If[ !IntegerQ[s]&&!PrimeQ[n], Print[n]], {n, 1, 256}]

CROSSREFS

Cf. A020492, A078538, A078539, A078540.

Sequence in context: A037130 A181298 A247121 * A084128 A044047 A296944

Adjacent sequences:  A078540 A078541 A078542 * A078544 A078545 A078546

KEYWORD

nonn

AUTHOR

Labos Elemer, Dec 04 2002

STATUS

approved

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Last modified November 15 14:06 EST 2019. Contains 329149 sequences. (Running on oeis4.)