OFFSET
0,4
COMMENTS
Isomorphism is up to permutation of the elements of the n-set.
LINKS
Andrew Howroyd, Table of n, a(n) for n = 0..50
EXAMPLE
In the following example the notation 211 corresponds to the fixed-point-free mapping {1->2, 2->1, 3->1}.
The a(3) = 9 nonisomorphic pairs of endofunctions are: {211, 211}, {211, 212}, {211, 231}, {211, 232}, {211, 311}, {211, 312}, {211, 332}, {231, 231}, {231, 312}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, May 10 2023
STATUS
approved