[seqfan] Re: unable to reproduce A152218 (sigma divisibility)

[Jack Brennen]

A152218 seems to be those numbers for which:

sigma_2(n)/sigma(n)/tau(n) is a square of a rational.

At least that definition agrees out through those first 8 terms.

That of course is a fairly different description that what is
actually shown there.  :)

Richard Mathar wrote:
> I can reproduce A152215, but the very similar A152218 seems to 
> be missing almost all terms:
> 
> http://oeis.org/classic/A152218
> Numbers such that sigma_2(n) * sigma(n) /tau(n) = integer
> 1, 4, 529, 2116, 2583, 3249, 3346, 6150
> What is a definition that matches the sequence?
> The formula says the same as the definition, so it is no aid.
> 
> The values sigma_2(n) * sigma(n) /tau(n) are
> 1, 15/2, 20, 49, 78, 150, 200, 1275/4, 1183/3, 585, 732, 980, 1190, 1500, 1560, 10571/5
> and most of these are integers
> 
> RJM
> 
> 
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