A162980 - cp's OEIS frontend

A162980 Triangle read by rows: T(n,k) is the number of reverse alternating (i.e., up-down) permutations of {1,2,...,n} having k fixed points (n >= 0, 0 <= k <= 1 + floor(n/2)).

n	a(n)
0	1
1	0
2	1
3	0
4	0
5	1
6	1
7	1
8	2
9	2
10	1
11	6
12	6
13	3
14	1
15	22
16	22
17	12
18	4
19	1
20	102
21	102
22	51
23	15
24	2
25	506
26	506
27	264
28	88
29	19
30	2
31	2952
32	2952
33	1476
34	458
35	89
36	9
37	18502
38	18502
39	9504
40	3168
41	726
42	110
43	9
44	131112
45	131112
46	65556
47	20868
48	4479
49	621
50	44
51	991226
52	991226
53	504864
54	168288
55	39696
56	6672
57	749
58	44

[1, 0, 1, 0, 0, 1, 1, 1, 2, 2, 1, 6, 6, 3, 1, 22, 22, 12, 4, 1, 102, 102, 51, 15, 2, 506, 506, 264, 88, 19, 2, 2952, 2952, 1476, 458, 89, 9, 18502, 18502, 9504, 3168, 726, 110, 9, 131112, 131112, 65556, 20868, 4479, 621, 44, 991226, 991226, 504864, 168288, 39696, 6672, 749, 44]

cp's OEIS Frontend

A162980 Triangle read by rows: T(n,k) is the number of reverse alternating (i.e., up-down) permutations of {1,2,...,n} having k fixed points (n >= 0, 0 <= k <= 1 + floor(n/2)).

Table of values

List of values