Narayana number

In combinatorics, the Narayana numbers N(n, k), n = 1, 2, 3 ..., 1 ≤ k ≤ n, form a triangular array of natural numbers, called Narayana triangle, that occur in various counting problems. They are named after Canadian mathematician T. V. Narayana (1930–1987). In combinatorics, the Narayana numbers N(n, k), n = 1, 2, 3 ..., 1 ≤ k ≤ n, form a triangular array of natural numbers, called Narayana triangle, that occur in various counting problems. They are named after Canadian mathematician T. V. Narayana (1930–1987). The Narayana numbers can be expressed in terms of binomial coefficients: