A162975 - cp's OEIS frontend

A162975 Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k doubledescents (0 <= k <= n-2). We say that i is a doubledescent (also called a double fall) of a permutation p if p(i) > p(i+1) > p(i+2).

n	a(n)
0	1
1	1
2	2
3	5
4	1
5	17
6	6
7	1
8	70
9	41
10	8
11	1
12	349
13	274
14	86
15	10
16	1
17	2017
18	2040
19	803
20	167
21	12
22	1
23	13358
24	16346
25	8221
26	2064
27	316
28	14
29	1
30	99377
31	143571
32	86214
33	28143
34	4961
35	597
36	16
37	1
38	822041
39	1365354
40	966114
41	374166
42	88482
43	11486
44	1138
45	18
46	1

[1, 1, 2, 5, 1, 17, 6, 1, 70, 41, 8, 1, 349, 274, 86, 10, 1, 2017, 2040, 803, 167, 12, 1, 13358, 16346, 8221, 2064, 316, 14, 1, 99377, 143571, 86214, 28143, 4961, 597, 16, 1, 822041, 1365354, 966114, 374166, 88482, 11486, 1138, 18, 1]

cp's OEIS Frontend

A162975 Triangle read by rows: T(n,k) is the number of permutations of {1,2,...,n} having k doubledescents (0 <= k <= n-2). We say that i is a doubledescent (also called a double fall) of a permutation p if p(i) > p(i+1) > p(i+2).

Table of values

List of values