OFFSET
0,3
COMMENTS
a(0) = 1 by convention.
Number of endofunctions on [2n] with two connected components of size n.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..193
EXAMPLE
a(1) = 1: 12.
MAPLE
a:= n-> `if`(n=0, 1, add(n^(n-j)*(n-1)!/(n-j)!, j=1..n)^2*binomial(2*n, n)/2):
seq(a(n), n=0..14);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Dec 15 2021
STATUS
approved