A172613 a(n) = (9n)!/(9!^n).

1, 1, 48620, 227873431500, 21452752266265320000, 19010638202652030712978200000, 101097362223624462291180422369532000000, 2392741010223442438553822446842770682716580000000, 203653377853981828616656775313699668953042169048889600000000

Offset: 0

Author

R. H. Hardin, Feb 06 2010

Keywords

• nonn
• easy

Comments

From Tilman Piesk, Oct 30 2014: (Start)

Column 9 of A187783.

Number of permutations of a multiset that contains n different elements, each occurring 9 times.

Or in other words (the former title of this sequence):

Number of 9*n X n 0..1 arrays with row sums 1 and column sums 9.

(End)

Examples

			a(3) = (9*3)!/(9!^3) = 227873431500 is the number of permutations of a multiset that contains 3 different elements, each occurring 9 times, e.g., {1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,3}.
		

Links

• Tilman Piesk, Table of n, a(n) for n = 0..54 (first 11 terms from R. H. Hardin)

Programs

Magma

[Factorial(9*n)/(362880^n): n in [0..20]]; // Vincenzo Librandi, Nov 01 2014

Maple

A172613:=n->(9*n)!/(362880^n): seq(A172613(n), n=0..10); # Wesley Ivan Hurt, Nov 01 2014

Mathematica

Table[(9 n)! / (362880^n), {n, 0, 10}] (* Vincenzo Librandi, Nov 01 2014 *)

Formula

a(n) = (9n)!/(9!^n).

Extensions

Name changed by Tilman Piesk, Oct 30 2014