A225942 - cp's OEIS frontend

A225942 Triangular array read by rows: T(n,k) is the number of f:{1,2,...,n}->{1,2,...,n} with exactly 2k elements that have a preimage of even (possibly zero) cardinality; n>=0, 0<=k<=floor(n/2).

n	a(n)
0	1
1	1
2	2
3	2
4	6
5	21
6	24
7	192
8	40
9	120
10	1800
11	1205
12	720
13	18000
14	25680
15	2256
16	5040
17	194040
18	489510
19	134953
20	40320
21	2257920
22	9031680
23	5196800
24	250496
25	362880
26	28304640
27	167015520
28	166793760
29	24943689
30	3628800
31	381024000
32	3149798400
33	4904524800
34	1514960640
35	46063360

[1, 1, 2, 2, 6, 21, 24, 192, 40, 120, 1800, 1205, 720, 18000, 25680, 2256, 5040, 194040, 489510, 134953, 40320, 2257920, 9031680, 5196800, 250496, 362880, 28304640, 167015520, 166793760, 24943689, 3628800, 381024000, 3149798400, 4904524800, 1514960640, 46063360]

cp's OEIS Frontend

A225942 Triangular array read by rows: T(n,k) is the number of f:{1,2,...,n}->{1,2,...,n} with exactly 2k elements that have a preimage of even (possibly zero) cardinality; n>=0, 0<=k<=floor(n/2).

Table of values

List of values