A267840 - cp's OEIS frontend

A267840 Number of symmetric difference-closed 4-sets consisting of the empty set and sets consisting of pairwise disjoint 2-subsets of {1,2,...,n}.

n	a(n)
1	0
2	0
3	0
4	3
5	15
6	105
7	525
8	3255
9	17703
10	112455
11	669735
12	4485195
13	29023995
14	205768563
15	1432735395
16	10728177915
17	79665069435
18	627587657595
19	4933313794683
20	40724759240235
21	336819780949995
22	2902978545030795
23	25135723046974155
24	225455477000793963

[0, 0, 0, 3, 15, 105, 525, 3255, 17703, 112455, 669735, 4485195, 29023995, 205768563, 1432735395, 10728177915, 79665069435, 627587657595, 4933313794683, 40724759240235, 336819780949995, 2902978545030795, 25135723046974155, 225455477000793963]

cp's OEIS Frontend

A267840 Number of symmetric difference-closed 4-sets consisting of the empty set and sets consisting of pairwise disjoint 2-subsets of {1,2,...,n}.

Table of values

List of values