[seqfan] Is the set of numbers representable by sum of 5 positive cubes in exactly 3 ways finite?

Sean A. Irvine sairvin at gmail.com
Thu May 13 05:21:46 CEST 2021


Hi all,

Dave Consiglio has been working to fill some holes in the OEIS around
sequences arising from sums of fixed numbers of like powers.  There are
some interesting cases arising, but I will mention just one sequence here.
A343705 is the set of numbers that are the sum of five positive cubes in
exactly three ways:

https://oeis.org/A343705

Could this sequence be finite?

Generating terms up to a(18984) = 2715466 is fairly easy (the b-file), but
thereafter we find no further terms with our simple search algorithms.

I could not see any literature result for this specific situation, but
surely this is something that has been studied.  Some analogous cases for
squares are known to be finite.

Sean.



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