[seqfan] unable to reproduce A152218 (sigma divisibility)
Richard Mathar
mathar at strw.leidenuniv.nl
Wed Aug 25 00:40:19 CEST 2010
I can reproduce A152215, but the very similar A152218 seems to
be missing almost all terms:
http://oeis.org/classic/A152218
Numbers such that sigma_2(n) * sigma(n) /tau(n) = integer
1, 4, 529, 2116, 2583, 3249, 3346, 6150
What is a definition that matches the sequence?
The formula says the same as the definition, so it is no aid.
The values sigma_2(n) * sigma(n) /tau(n) are
1, 15/2, 20, 49, 78, 150, 200, 1275/4, 1183/3, 585, 732, 980, 1190, 1500, 1560, 10571/5
and most of these are integers
RJM
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