A078543 Balanced refactorable numbers.

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

Offset: 1

Author

Labos Elemer, Dec 04 2002

Keywords

• nonn

Examples

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

Links

• Amiram Eldar, Table of n, a(n) for n = 1..10000 (calculated using data from Jud McCranie, terms 1..500 from Donovan Johnson)

Crossrefs

Intersection of A033950 and A020492.

Cf. A078538, A078539, A078540.

Programs

Mathematica

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