[seqfan] Re: sigma(odd square) = odd square

[M. F. Hasler]

Max,
in case you submit your list, please cross-reference A234641
<https://oeis.org/A234641> which contains this list as subsequence.
- Maximilian

On Sat, Feb 13, 2016 at 5:46 PM, Max Alekseyev wrote:

> Here are all odd squarefree numbers m such that the prime divisors of both
> m and sigma(m^2) are below 300 and sigma(m^2) is an odd square.
>
> [1, 247863, 469623, 985369, 1933815, 2181409, 14142695, 41193543, 52256985,
> 63355655, 78048903, 94799985, 22535428895, 53257909705, 100907111305,
> 100952955455, 135545609265, 245894816265, 449134850879, 814780591079,
> 1093974229257, 1905521352735, 2149492804921, 4218441445335, 4900724638953,
> 8851187928505, 16770237706105, 1164978366136871, 1743174017143377,
> 2113400373846671, 7808973582128433, 4156721428548303615]
>
> If I increase the bound for prime divisors from 300 to 1000, then there are
> 2^16 = 65536 such numbers.
>
> Regards,
> Max
>
>
> On Sat, Feb 13, 2016 at 3:13 PM, Zak Seidov wrote:
>
> >  Just found:
> > sigma (1476326929 = 7^2*11^2*499^2) = 1891467081 = 3^2*7^2*19^2*109^2.
> > Next one?
> >
> >
> > >Суббота, 13 февраля 2016, 23:05 +03:00 от Zak Seidov <zakseidov at mail.ru
> >:
> > >
> > >
> > >Are 1 and 81 the only odd squares with odd square sigma:
> > >sigma(1)=1 and sigma(81)=121?
> > >--
> > >Zak  Seidov
>