A090758 Numbers k which occur exactly twice in A001600.
5, 13, 15, 17, 19, 24, 29, 37, 44, 45, 46, 47, 61, 73, 75, 85, 86, 87, 99, 105, 107, 144, 145, 149, 171, 173, 186, 187, 197, 203, 205, 224, 245, 252, 270, 272, 276, 279, 282, 284
Offset: 1
Examples
k = 61 is a term because m*tau(m)/sigma(m) = 61 if and only if m = 2^30 * 61 * (2^31-1) or m = 2^60 * (2^61-1). - _Jinyuan Wang_, Mar 05 2020
Links
- T. Goto and S. Shibata, All numbers whose positive divisors have integral harmonic mean up to 300, Math. Comput. 73 (2004), 475-491.