A317555 - cp's OEIS frontend

A317555 Triangle read by rows: T(n,k) is the number of preimages of the permutation 21345...n under West's stack-sorting map that have k+1 valleys (1 <= k <= floor((n-1)/2)).

n	a(n)
3	1
4	4
5	12
6	2
7	32
8	16
9	80
10	80
11	5
12	192
13	320
14	60
15	448
16	1120
17	420
18	14
19	1024
20	3584
21	2240
22	224
23	2304
24	10752
25	10080
26	2016
27	42
28	5120
29	30720
30	40320
31	13440
32	840
33	11264
34	84480
35	147840
36	73920
37	9240
38	132
39	24576
40	225280
41	506880
42	354816
43	73920
44	3168

[1, 4, 12, 2, 32, 16, 80, 80, 5, 192, 320, 60, 448, 1120, 420, 14, 1024, 3584, 2240, 224, 2304, 10752, 10080, 2016, 42, 5120, 30720, 40320, 13440, 840, 11264, 84480, 147840, 73920, 9240, 132, 24576, 225280, 506880, 354816, 73920, 3168]

cp's OEIS Frontend

A317555 Triangle read by rows: T(n,k) is the number of preimages of the permutation 21345...n under West's stack-sorting map that have k+1 valleys (1 <= k <= floor((n-1)/2)).

Table of values

List of values