A255907 Number of collections of nonempty multisets with a total of 2n objects of exactly n colors.

1, 2, 23, 492, 15800, 693667, 39371078, 2780643510, 237625842970, 24048952078889, 2833749745048664, 383425910861623475, 58894162142705623291, 10170230140575830362828, 1958227054977871232165423, 417406876191416533261184253, 97882032782014459518083172751

Offset: 0

Author

Alois P. Heinz, Mar 10 2015

Keywords

• nonn

Examples

			a(0) = 1: {}.
a(1) = 2: {{1},{1}}, {{1,1}}.
a(2) = 23: {{1},{1},{1},{2}}, {{1},{1},{2},{2}}, {{1},{2},{2},{2}}, {{1},{1},{1,2}}, {{1},{1},{2,2}}, {{1},{2},{1,1}}, {{1},{2},{1,2}}, {{1},{2},{2,2}}, {{2},{2},{1,1}}, {{2},{2},{1,2}}, {{1,1},{1,2}}, {{1,1},{2,2}}, {{1,2},{1,2}}, {{1,2},{2,2}}, {{1},{1,1,2}}, {{1},{1,2,2}}, {{1},{2,2,2}}, {{2},{1,1,1}}, {{2},{1,1,2}}, {{2},{1,2,2}}, {{1,1,1,2}}, {{1,1,2,2}}, {{1,2,2,2}}.
		

Links

• Alois P. Heinz, Table of n, a(n) for n = 0..200

Crossrefs

Cf. A255903.

Formula

a(n) = A255903(2n,n).