A268222 - cp's OEIS frontend

A268222 Triangle read by rows: T(n,k) (n>=5, k=3..n-2) 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 {0,4,5,6,...,s,n} where s is the size of the largest proper open set in t.

n	a(n)
5	5
6	15
7	30
8	35
9	105
10	210
11	70
12	280
13	840
14	1680
15	126
16	630
17	2520
18	7560
19	15120
20	210
21	1260
22	6300
23	25200
24	75600
25	151200
26	330
27	2310
28	13860
29	69300
30	277200
31	831600
32	1663200
33	495
34	3960
35	27720
36	166320
37	831600
38	3326400
39	9979200
40	19958400
41	715
42	6435
43	51480
44	360360
45	2162160
46	10810800
47	43243200
48	129729600
49	259459200

[5, 15, 30, 35, 105, 210, 70, 280, 840, 1680, 126, 630, 2520, 7560, 15120, 210, 1260, 6300, 25200, 75600, 151200, 330, 2310, 13860, 69300, 277200, 831600, 1663200, 495, 3960, 27720, 166320, 831600, 3326400, 9979200, 19958400, 715, 6435, 51480, 360360, 2162160, 10810800, 43243200, 129729600, 259459200]

cp's OEIS Frontend

A268222 Triangle read by rows: T(n,k) (n>=5, k=3..n-2) 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 {0,4,5,6,...,s,n} where s is the size of the largest proper open set in t.

Table of values

List of values