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
The a(3)=2 nonisomorphic pairs of derangements with permutations shown in cycle notation are:
{(123), (123)},
{(123), (132)}.
The a(4)=7 nonisomorphic pairs of derangements are:
{(12)(34), (12)(34)},
{(12)(34), (13)(24)},
{(12)(34), (1234)},
{(12)(34), (1324)},
{(1234), (1234)},
{(1234), (1243)},
{(1234), (1432)}.
CROSSREFS
KEYWORD
nonn
AUTHOR
Andrew Howroyd, May 02 2023
STATUS
approved