On the Total Positivity of Delannoy-Like Triangles
Lili Mu
School of Mathematics
Liaoning Normal University
Dalian, 116029
PR China
Sai-nan Zheng
School of Mathematical Sciences
Dalian University of Technology
Dalian, 116024
PR China
Abstract:
Define an infinite lower triangular matrix
D(e,h) = [dn,k]n,k ≥ 0 by the
recurrence d0,0 = d1,0 = d1,1 = 1,
dn,k =
dn-1,k-1 + edn-1,k +
hdn-2,k-1,
where e, h are both nonnegative and dn,k = 0 unless n ≥ k ≥ 0. We call
D(e, h) the Delannoy-like triangle.
The entries dn,k count lattice
paths from (0, 0) to (n - k, k)
using the steps (0, 1), (1, 0) and (1, 1)
with assigned weights 1, e, and h. Some well-known combinatorial
triangles are such matrices, including the Pascal triangle D(1, 0), the
Fibonacci triangle D(0, 1), and the Delannoy triangle D(1, 1).
Futhermore, the Schröder triangle and Catalan triangle also arise as
inverses of Delannoy-like triangles. Here we investigate the total
positivity of Delannoy-like triangles. In addition, we show that each
row and diagonal of Delannoy-like triangles are all PF sequences.
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(Concerned with sequences
A001850
A007318
A008288
A026729
A033184
A132372.)
Received June 29 2016; revised version received December 20 2016.
Published in Journal of Integer Sequences, December 26 2016.
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