[seqfan] Re: Question on 2F1 from Karol A. Penson

Richard Guy rkg at cpsc.ucalgary.ca
Tue Jul 16 19:15:52 CEST 2013


Dear OEIS,
           I was about to submit seq A146556 but found that it was already 
in.
           The formula, and its appearance in the PARI program, is more 
neatly written  a(n)=2*sigma(a(n-1))-a(n-1).

           The example, 1488, 2480, 3472, 4464, 8432, 9424, continues
10416, 21328, 22320, 55056, ..., seems not to be in OEIS.  Curiously,
the first term where it might be in doubt is the 31st.

           It would be good if all aliquot sequences, and also
divisibility sequences, were available in factored form, but I can
understand why this is not so.  If anyone would like the first few
hundred terms of A146556 with their factors, I can send.  My
labelling is from zero, so the first term containing a factor 31
is the 30th.  R.





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