Abstract:
The famous story of the number 1729, the smallest integer which can be expressed
as the sum of two positive cubes in two different ways, motivated the
introduction of Taxicab Numbers. The smallest number expressible as the sum of
two cubes in n different ways is called Taxicab(n). So, Taxicab(2) = 1729. Further
on, Taxicab(5) = 48988659276962496. Computing Taxicab(n) is challenging and
interesting, both from mathematical and programming points of view.
The exact value of Taxicab(6) is not known; in view of the results obtained
by Bernstein [1] and Rathbun [14] it follows that Taxicab(6) is in the interval
[10¹⁸, 24153319581254312065344]. In [5] we proved that with probability greater
than 99%, Taxicab(6) = 24153319581254312065344.
In this note we improve the method used in [5] in two ways: we use (1) a larger,
and (2) a better quality random sampling, namely, a sample of 562,500 quantum
random integers drawn from the above mentioned interval using Quantis, [10]. As a
result, we prove that the above value for Taxicab(6) is true with probability greater
than 99.8%.