A277083 - cp's OEIS frontend

A277083 Irregular triangle read by rows: T(n,k) = number of size k subsets of S_n that remain unchanged by a rotation of 180 degrees.

n	a(n)
0	1
1	1
2	1
3	1
4	1
5	2
6	1
7	1
8	2
9	3
10	4
11	3
12	2
13	1
14	1
15	8
16	36
17	120
18	322
19	728
20	1428
21	2472
22	3823
23	5328
24	6728
25	7728
26	8092
27	7728
28	6728
29	5328
30	3823
31	2472
32	1428
33	728
34	322
35	120
36	36
37	8
38	1
39	1
40	8
41	84
42	504
43	3178
44	15512
45	74788
46	311144
47	1252819
48	4577328
49	16087512
50	52691408
51	165911284

[1, 1, 1, 1, 1, 2, 1, 1, 2, 3, 4, 3, 2, 1, 1, 8, 36, 120, 322, 728, 1428, 2472, 3823, 5328, 6728, 7728, 8092, 7728, 6728, 5328, 3823, 2472, 1428, 728, 322, 120, 36, 8, 1, 1, 8, 84, 504, 3178, 15512, 74788, 311144, 1252819, 4577328, 16087512, 52691408, 165911284]

cp's OEIS Frontend

A277083 Irregular triangle read by rows: T(n,k) = number of size k subsets of S_n that remain unchanged by a rotation of 180 degrees.

Table of values

List of values