A206823 - cp's OEIS frontend

A206823 Triangular array read by rows: T(n,k) is the number of functions f:{1,2,...,n}->{1,2,...,n} with exactly k elements x such that |f^(-1)(x)| = 1; n>=0, 0<=k<=n.

n	a(n)
0	1
1	0
2	1
3	2
4	0
5	2
6	3
7	18
8	0
9	6
10	40
11	48
12	144
13	0
14	24
15	205
16	1000
17	600
18	1200
19	0
20	120
21	2556
22	7380
23	18000
24	7200
25	10800
26	0
27	720
28	24409
29	125244
30	180810
31	294000
32	88200
33	105840
34	0
35	5040
36	347712
37	1562176
38	4007808
39	3857280
40	4704000
41	1128960
42	1128960
43	0
44	40320

[1, 0, 1, 2, 0, 2, 3, 18, 0, 6, 40, 48, 144, 0, 24, 205, 1000, 600, 1200, 0, 120, 2556, 7380, 18000, 7200, 10800, 0, 720, 24409, 125244, 180810, 294000, 88200, 105840, 0, 5040, 347712, 1562176, 4007808, 3857280, 4704000, 1128960, 1128960, 0, 40320]

cp's OEIS Frontend

A206823 Triangular array read by rows: T(n,k) is the number of functions f:{1,2,...,n}->{1,2,...,n} with exactly k elements x such that |f^(-1)(x)| = 1; n>=0, 0<=k<=n.

Table of values

List of values