Delannoy_number
Delannoy number
Number of paths between grid corners, allowing diagonal steps
In mathematics, a Delannoy number describes the number of paths from the southwest corner (0, 0) of a rectangular grid to the northeast corner (m, n), using only single steps north, northeast, or east. The Delannoy numbers are named after French army officer and amateur mathematician Henri Delannoy.[1]
The Delannoy number also counts the number of global alignments of two sequences of lengths and ,[2] the number of points in an m-dimensional integer lattice or cross polytope which are at most n steps from the origin,[3] and, in cellular automata, the number of cells in an m-dimensional von Neumann neighborhood of radius n[4] while the number of cells on a surface of an m-dimensional von Neumann neighborhood of radius n is given with (sequence A266213 in the OEIS).