OFFSET
0,3
COMMENTS
a(n) is the number of ordered pairs (p, f) such that p f = f p, where p is a permutation and f is an endofunction.
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..382
Math Overflow, What is the probability two random maps on n symbols commute?, 2013.
FORMULA
a(n) = n! * A001372(n). - Joerg Arndt, Feb 01 2015
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Martin Fuller, Feb 01 2015
STATUS
approved