0466132人目の素数さん
2018/03/15(木) 00:14:53.90ID:27Ebyr8J(M+n+1)(M+n)(M+n-1)…(M+2)・(M+n)(M+n-1)(M+n-2)…(M+1) / (n+1)n(n-1)…2・n(n-1)(n-2)…1
Enumerative Combinatorics volume 1 second edition. Richard P. Stanley ( http://math.mit.edu/~rstan/ec/ec1.pdf )
Exercise 3.172