Seeds for Generalized Taxicab Numbers
Jeffrey H. Dinitz
University of Vermont
Burlington, VT 05405
USA
Richard A. Games
Mitre Corporation
Bedford, MA 01730
USA
Robert L. Roth
Department of Mathematics
Emory University
Atlanta, GA 30322
USA
Abstract:
The generalized taxicab number T(n,m,t)
is equal to the smallest number that is the sum of n
positive mth powers in t ways. This definition is
inspired by Ramanujan's observation that 1729 = 13+123 = 93+103 is
the smallest number that is the sum of two cubes in two ways and
thus 1729 = T(2, 3, 2). In this paper we prove that for any
given positive integers m and t, there exists a number
s such that T(s+k,m,t) =
T(s,m,t)+k for every k ≥
0. The smallest such s is termed the seed for the generalized
taxicab number. Furthermore, we find explicit expressions for this seed
number when the number of ways t is 2 or 3 and present a conjecture
for t ≥ 4 ways.
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(Concerned with sequence
A011541.)
Received January 25 2019; revised versions received May 3 2019; May 6 2019.
Published in Journal of Integer Sequences,
May 17 2019.
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