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Lattice path of length 5 in ℤ 2 with S = { (2,0), (1,1), (0,-1) }.. In combinatorics, a lattice path L in the d-dimensional integer lattice of length k with steps in the set S, is a sequence of vectors ,, …, such that each consecutive difference lies in S. [1]
In mathematics, the Schröder number, also called a large Schröder number or big Schröder number, describes the number of lattice paths from the southwest corner (,) of an grid to the northeast corner (,), using only single steps north, (,); northeast, (,); or east, (,), that do not rise above the SW–NE diagonal.
C n is the number of monotonic lattice paths along the edges of a grid with n × n square cells, which do not pass above the diagonal. A monotonic path is one which starts in the lower left corner, finishes in the upper right corner, and consists entirely of edges pointing rightwards or upwards.
An n-path from an n-tuple (,, …,) of vertices of G to an n-tuple (,, …,) of vertices of G will mean an n-tuple (,, …,) of paths in G, with each leading from to . This n -path will be called non-intersecting just in case the paths P i and P j have no two vertices in common (including endpoints) whenever i ≠ j {\displaystyle i\neq j} .
The Narayana numbers also count the number of lattice paths from (,) to (,), with steps only northeast and southeast, not straying below the x-axis, with peaks. The following figures represent the Narayana numbers N ( 4 , k ) {\displaystyle \operatorname {N} (4,k)} , illustrating the above mentioned symmetries.
The closely related large Schröder numbers are equal to twice the Schröder–Hipparchus numbers, and may also be used to count several types of combinatorial objects including certain kinds of lattice paths, partitions of a rectangle into smaller rectangles by recursive slicing, and parenthesizations in which a pair of parentheses surrounding the whole sequence of elements is also allowed.
63 Delannoy paths through a 3 × 3 grid. The octahedron in the three-dimensional integer lattice, whose number of lattice points is counted by the centered octahedral number, is a metric ball for three-dimensional taxicab geometry, a geometry in which distance is measured by the sum of the coordinatewise distances rather than by Euclidean distance.
The Delannoy number (,) also counts the global alignments of two sequences of lengths and , [2] the 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 cells in an m-dimensional von Neumann neighborhood of radius n.