A282507 - cp's OEIS frontend

A282507 Triangular array read by rows. T(n,k) is the number of chain topologies on an n-set with exactly k open sets where one of the open sets is a single point set, n >= 2, 3 <= k <= n+1.

n	a(n)
2	2
3	3
4	6
5	4
6	24
7	24
8	5
9	70
10	180
11	120
12	6
13	180
14	900
15	1440
16	720
17	7
18	434
19	3780
20	10920
21	12600
22	5040
23	8
24	1008
25	14448
26	67200
27	134400
28	120960
29	40320
30	9
31	2286
32	52164
33	367416
34	1134000
35	1723680
36	1270080
37	362880
38	10
39	5100
40	181500
41	1864800
42	8341200
43	19051200
44	23284800
45	14515200
46	3628800

[2, 3, 6, 4, 24, 24, 5, 70, 180, 120, 6, 180, 900, 1440, 720, 7, 434, 3780, 10920, 12600, 5040, 8, 1008, 14448, 67200, 134400, 120960, 40320, 9, 2286, 52164, 367416, 1134000, 1723680, 1270080, 362880, 10, 5100, 181500, 1864800, 8341200, 19051200, 23284800, 14515200, 3628800]

cp's OEIS Frontend

A282507 Triangular array read by rows. T(n,k) is the number of chain topologies on an n-set with exactly k open sets where one of the open sets is a single point set, n >= 2, 3 <= k <= n+1.

Table of values

List of values