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

1,1

Links

Table of n, a(n) for n=1..40.

T. Goto and S. Shibata, All numbers whose positive divisors have integral harmonic mean up to 300, Math. Comput. 73 (2004), 475-491.

Example

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

Crossrefs

Cf. A001600, A090240.

Sequence in context: A174069 A020996 A090759 * A327922 A309812 A324909

Adjacent sequences: A090755 A090756 A090757 * A090759 A090760 A090761

Keyword

nonn,more

Author

R. K. Guy, Feb 08 2004

Status

approved