[seqfan] Re: Number of solutions of sigma(x) = n.

Charles Greathouse charles.greathouse at case.edu
Wed May 14 08:28:13 CEST 2014


This is A054973; sigma(6) = 12, not 6. (And I don't think we're ready for
A250000 yet.)

Charles Greathouse
Analyst/Programmer
Case Western Reserve University


On Tue, May 13, 2014 at 4:04 PM, Allan Wechsler <acwacw at gmail.com> wrote:

> If I have done this right, the first few entries are 1, 0, 1, 1, 0, 2, 1,
> 1, 0, 0. For example, a(6) = 2 because sigma(5) = sigma(6) = 6, and a(24) =
> 3 because sigma(14) = sigma(15) = sigma(23) = 24.
>
> If my paper calculations were right for the first few entries, I am really
> surprised to find this missing from OEIS, and am inclined to nominate it
> for sequence A250000. It has many links with existing sequences relating to
> sums of divisors.
>
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