A280889 Number of set partitions of [2n] into exactly n blocks where sizes of distinct blocks are coprime.

1, 1, 4, 75, 56, 6930, 28512, 2849847, 972400, 693870606, 99936200, 63488350926, 475814969280, 166184959669300, 497980728000, 78877488833249175, 1489333512849120, 1116126129558913110, 1597083864660900000, 4467282986266589095530, 107279471180408841600

Offset: 0

Author

Alois P. Heinz, Jan 09 2017

Keywords

• nonn

Examples

			a(1) = 1: 12.
a(2) = 4: 123|4, 124|3, 134|2, 1|234.
a(4) = 56 = binomial(8,3): 12345|6|7|8, 12346|5|7|8, 12347|5|6|8, ..., 1|25678|3|4, 1|2|35678|4, 1|2|3|45678.
		

Links

• Wikipedia, Coprime integers
• Wikipedia, Partition of a set

Crossrefs

Cf. A280880.

Formula

a(n) = A280880(2n,n).