A174764 - cp's OEIS frontend

A174764 Sum of the numerators for computing the second moment of the probability mass function (PMF) of the number of 2-cycles in the involutions on n elements (A000085) assuming the involutions are all equally likely.

n	a(n)
1	0
2	1
3	3
4	18
5	70
6	330
7	1386
8	6328
9	28008
10	130140
11	603460
12	2895816
13	14024088
14	69786808
15	352043160
16	1817317440
17	9525774016
18	50958843408
19	276906491568
20	1532719442080
21	8615750596320
22	49260355141536
23	285887468809888

[0, 1, 3, 18, 70, 330, 1386, 6328, 28008, 130140, 603460, 2895816, 14024088, 69786808, 352043160, 1817317440, 9525774016, 50958843408, 276906491568, 1532719442080, 8615750596320, 49260355141536, 285887468809888]

cp's OEIS Frontend

A174764 Sum of the numerators for computing the second moment of the probability mass function (PMF) of the number of 2-cycles in the involutions on n elements (A000085) assuming the involutions are all equally likely.

Table of values

List of values