A268223 - cp's OEIS frontend

A268223 Triangle read by rows: T(n,k) (n>=6, k=3..n-3) is the number of topologies t on n points having exactly k open sets such that t contains exactly one open set of size m for each m in {0,5,6,7,...,s,n} where s is the size of the largest proper open set in t.

n	a(n)
6	6
7	21
8	42
9	56
10	168
11	336
12	126
13	504
14	1512
15	3024
16	252
17	1260
18	5040
19	15120
20	30240
21	462
22	2772
23	13860
24	55440
25	166320
26	332640
27	792
28	5544
29	33264
30	166320
31	665280
32	1995840
33	3991680
34	1287
35	10296
36	72072
37	432432
38	2162160
39	8648640
40	25945920
41	51891840

[6, 21, 42, 56, 168, 336, 126, 504, 1512, 3024, 252, 1260, 5040, 15120, 30240, 462, 2772, 13860, 55440, 166320, 332640, 792, 5544, 33264, 166320, 665280, 1995840, 3991680, 1287, 10296, 72072, 432432, 2162160, 8648640, 25945920, 51891840]

cp's OEIS Frontend

A268223 Triangle read by rows: T(n,k) (n>=6, k=3..n-3) is the number of topologies t on n points having exactly k open sets such that t contains exactly one open set of size m for each m in {0,5,6,7,...,s,n} where s is the size of the largest proper open set in t.

Table of values

List of values