Let k >= 3 be an odd integer. Consider the k-generalized Fibonacci sequence backward.
The characteristic polynomial of this sequence has no dominating zero, therefore the
application of Baker's method becomes more difficult. In this paper, we investigate
the coincidence of the absolute values of two terms. The principal theorem gives a
lower bound for the difference of two terms (in absolute value) if the larger subscript
of the two terms is large enough. A corollary of this theorem makes possible to bound
the coincidences in the sequence. The proof essentially depends on the structure of
the zeros of the characteristic polynomial, and on the application of linear forms
in the logarithms of algebraic numbers. Then we reduced the theoretical bound in practice
for 3 <= k <= 99, and determined all the coincidences in the corresponding sequences.
Finally, we explain certain patterns of pairwise occurrences in each sequence depending
on k if k exceeds a suitable entry value associated to the pair.