Powers of Two as Sums of Two Lucas Numbers
Jhon J. Bravo
Mathematics Department
University of Cauca
Street 5 No. 4-70
Popayán, Cauca
Colombia
Florian Luca
School of Mathematics
University of the Witwatersrand
P. O. Box Wits 2050
South Africa
and
Mathematical Institute
UNAM Juriquilla
Santiago de Querétaro 76230
Querétaro de Arteaga
Mexico
Abstract:
Let (Ln)n ≥ 0
be the Lucas sequence given by L0 = 0,
L1 = 1,
and Ln+2 =
Ln+1 +
Ln for n ≥ 0.
In this paper, we are interested in finding all
powers of two which are sums of two Lucas numbers, i.e., we study the
Diophantine equation
Ln +
Lm = 2a
in nonnegative integers
n, m, and a.
The proof of our main theorem uses lower bounds for linear forms in
logarithms, properties of continued fractions, and a version of the
Baker-Davenport reduction method in diophantine approximation. This
paper continues our previous work where we obtained a similar result
for the Fibonacci numbers.
Full version: pdf,
dvi,
ps,
latex
(Concerned with sequences
A000032
A000045.)
Received March 17 2014;
revised versions received July 22 2014; July 30 2014.
Published in Journal of Integer Sequences, July 30 2014.
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