Triangles of numbers | Integer sequences | Factorial and binomial topics | Enumerative combinatorics
Eulerian number
In combinatorics, the Eulerian number A(n, m) is the number of permutations of the numbers 1 to n in which exactly m elements are greater than the previous element (permutations with m "ascents"). They are the coefficients of the Eulerian polynomials: The Eulerian polynomials are defined by the exponential generating function The Eulerian polynomials can be computed by the recurrence An equivalent way to write this definition is to set the Eulerian polynomials inductively by Other notations for A(n, m) are E(n, m) and . (Wikipedia).
