[seqfan] Re: A151659

franktaw at netscape.net franktaw at netscape.net
Mon Jun 22 21:03:22 CEST 2009


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.

I will next submit the sequence for the odd part of UnitarySigma(n).  
(This really should  have been added when A151659 was added!)

Franklin T. Adams-Watters




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