[seqfan] Re: A151659

[Robert Gerbicz]

2009/6/22 <franktaw at netscape.net>

> I have just submitted A161942, the odd part of sigma(n).
>
> I apparently only checked up to 2 million last time; up to 20 million,
> there are two odd numbers with a(n) and a(a(n)) both >= n: 81 and
> 18966025, which is 5^2*13^2*67^2.  Both fall off rapidly from that
> point.
>
>
Hi!

All terms up to 10^10:
1
81
18966025
135187129
164275489
350561925
445421025
598047025
649587169
748733769
850830561
960362325
1055925025
1341097641
1406175001
1476326929
1520766009
1536248025
1591004025
1735566525
1753206525
1756196649
1798692921
1831175325
1895122089
2100297241
2766234025
3237951409
3280883841
3343961929
3758303025
4046868225
4558583925
4877485921
5558746249
5822758249
6518140225
6745097205
6826229641
8130087889
8766517725
9303181209
9999000025