A331477 Number of n element multisets of n element multisets of an n-set.

1, 1, 6, 220, 73815, 286243776, 13949678575756, 8800321588119330984, 73241437035618231162682185, 8183604949527627465377060678018870, 12477686558866630120430437118910496237274716, 263383624455446425760290611316122951917033704595478840

Offset: 0

Author

Andrew Howroyd, Jan 17 2020

Keywords

• nonn

Examples

			The a(2) = 6 multisets are:
   {{1,1}, {1,1}},
   {{1,1}, {1,2}},
   {{1,1}, {2,2}},
   {{1,2}, {1,2}},
   {{1,2}, {2,2}},
   {{2,2}, {2,2}}.
		

Links

• Andrew Howroyd, Table of n, a(n) for n = 0..40

Crossrefs

Main diagonal of A331436.

Programs

Mathematica

Table[Binomial[Binomial[2n-1,n]+n-1,n],{n,0,20}] (* Harvey P. Dale, Aug 19 2021 *)

PARI

a(n)={binomial(binomial(2*n - 1, n) + n - 1, n)}

Formula

a(n) = binomial(binomial(2*n - 1, n) + n - 1, n).