Numeric.Combinatorics

This provides a few facilities for working with common combinatorial functions.

Documentation

choose :: Int -> Int -> IO Integer

See here.

doubleFactorial :: Int -> IO Integer

See here.

catalan :: Int -> IO Integer

The nth Catalan number, with indexing beginning at 0. See here.

λ:> mapM catalan [0..9]
[1,1,2,5,14,42,132,429,1430,4862]

factorial :: Int -> IO Integer