A268217 - cp's OEIS frontend

A268217 Triangle read by rows: T(n,k) (n>=3, k=3..n) 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 {0,2,3,4,...,s,n} where s is the size of the largest proper open set in t.

n	a(n)
3	3
4	6
5	12
6	10
7	30
8	60
9	15
10	60
11	180
12	360
13	21
14	105
15	420
16	1260
17	2520
18	28
19	168
20	840
21	3360
22	10080
23	20160
24	36
25	252
26	1512
27	7560
28	30240
29	90720
30	181440
31	45
32	360
33	2520
34	15120
35	75600
36	302400
37	907200
38	1814400
39	55
40	495
41	3960
42	27720
43	166320
44	831600
45	3326400
46	9979200
47	19958400

[3, 6, 12, 10, 30, 60, 15, 60, 180, 360, 21, 105, 420, 1260, 2520, 28, 168, 840, 3360, 10080, 20160, 36, 252, 1512, 7560, 30240, 90720, 181440, 45, 360, 2520, 15120, 75600, 302400, 907200, 1814400, 55, 495, 3960, 27720, 166320, 831600, 3326400, 9979200, 19958400]

cp's OEIS Frontend

A268217 Triangle read by rows: T(n,k) (n>=3, k=3..n) 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 {0,2,3,4,...,s,n} where s is the size of the largest proper open set in t.

Table of values

List of values