A368730 - cp's OEIS frontend

A368730 Number of n-element sets of singletons or pairs of distinct elements of {1..n} with union {1..n}, or loop-graphs covering n vertices with n edges, such that it is not possible to choose a different element from each.

n	a(n)
0	0
1	0
2	0
3	0
4	6
5	180
6	4560
7	117600
8	3234588
9	96119982
10	3092585310
11	107542211535
12	4029055302855
13	162040513972623
14	6970457656110039
15	319598974394563500
16	15568332397812799920
17	803271954062642638830
18	43778508937914677872788
19	2513783434620146896920843

[0, 0, 0, 0, 6, 180, 4560, 117600, 3234588, 96119982, 3092585310, 107542211535, 4029055302855, 162040513972623, 6970457656110039, 319598974394563500, 15568332397812799920, 803271954062642638830, 43778508937914677872788, 2513783434620146896920843]

cp's OEIS Frontend

A368730 Number of n-element sets of singletons or pairs of distinct elements of {1..n} with union {1..n}, or loop-graphs covering n vertices with n edges, such that it is not possible to choose a different element from each.

Table of values

List of values