A319029 - cp's OEIS frontend

A319029 Triangle read by rows: T(n,k) is the number of permutations pi of [n] such that pi has k descents and s(pi) avoids the patterns 132 and 321, where s is West's stack-sorting map (0 <= k <= n-1).

n	a(n)
1	1
2	1
3	1
4	1
5	4
6	1
7	1
8	10
9	10
10	1
11	1
12	20
13	46
14	20
15	1
16	1
17	35
18	146
19	146
20	35
21	1
22	1
23	56
24	371
25	666
26	371
27	56
28	1
29	1
30	84
31	812
32	2290
33	2290
34	812
35	84
36	1
37	1
38	120
39	1596
40	6504
41	10198
42	6504
43	1596
44	120
45	1
46	1
47	165
48	2892
49	16080
50	36352
51	36352
52	16080
53	2892
54	165
55	1

[1, 1, 1, 1, 4, 1, 1, 10, 10, 1, 1, 20, 46, 20, 1, 1, 35, 146, 146, 35, 1, 1, 56, 371, 666, 371, 56, 1, 1, 84, 812, 2290, 2290, 812, 84, 1, 1, 120, 1596, 6504, 10198, 6504, 1596, 120, 1, 1, 165, 2892, 16080, 36352, 36352, 16080, 2892, 165, 1]

cp's OEIS Frontend

A319029 Triangle read by rows: T(n,k) is the number of permutations pi of [n] such that pi has k descents and s(pi) avoids the patterns 132 and 321, where s is West's stack-sorting map (0 <= k <= n-1).

Table of values

List of values