J. Integer Seq. 6(1), Art. 03.1.5, 19 p., electronic only (2003)
Summary
Summary: The central Delannoy numbers, d_n_n >=0 = 1,3,13,63,321, 1683, 8989, 48639,$ \dots $(A001850 of $\it $The On-Line Encyclopedia of Integer Sequences) will be defined so that d_n counts the lattice paths running from (0,0) to $(n,n)$ that use the steps (1,0), (0,1), and (1,1). In a recreational spirit we give a collection of 29 configurations that these numbers count.
