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

[Max Alekseyev]

Hi Maximilian,
I'm not going to submit this list as it is constructed under rather
arbitrary constraints. The list is useful for verifications of other
methods, or to illustrate large terms of the corresponding sequences.
Max

On Mon, Feb 15, 2016 at 9:06 AM, M. F. Hasler <oeis at hasler.fr> wrote:

> 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
> >
>
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