  Menon's proof of the preservation of log-concavity of sequences under
convolution becomes simpler when adapted to 2-sided infinite sequences. Under
assumption of log-concavity of two 2-sided infinite sequences, the existence of
the convolution is characterised by a convergence criterion. Preservation of
log-concavity under convolution yields a method of establishing the
log-concavity of rows of a large class of Pascal type triangles, including a
weighted generalization of the Delannoy triangle. This method is also compared
with known techniques of proving log-concavity.
