A108431 - cp's OEIS frontend

A108431 Triangle read by rows: T(n,k) is number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1),U=(1,2), or d=(1,-1) and have k hills (a hill is either a ud or a Udd starting at the x-axis).

n	a(n)
0	1
1	0
2	2
3	6
4	0
5	4
6	34
7	24
8	0
9	8
10	274
11	136
12	72
13	0
14	16
15	2266
16	1168
17	408
18	192
19	0
20	32
21	19738
22	9880
23	3720
24	1088
25	480
26	0
27	64
28	177642
29	87840
30	32088
31	10496
32	2720
33	1152
34	0
35	128
36	1640050
37	802216
38	291048
39	92096
40	27680
41	6528
42	2688
43	0
44	256
45	15445690
46	7492240

[1, 0, 2, 6, 0, 4, 34, 24, 0, 8, 274, 136, 72, 0, 16, 2266, 1168, 408, 192, 0, 32, 19738, 9880, 3720, 1088, 480, 0, 64, 177642, 87840, 32088, 10496, 2720, 1152, 0, 128, 1640050, 802216, 291048, 92096, 27680, 6528, 2688, 0, 256, 15445690, 7492240]

cp's OEIS Frontend

A108431 Triangle read by rows: T(n,k) is number of paths from (0,0) to (3n,0) that stay in the first quadrant (but may touch the horizontal axis), consisting of steps u=(2,1),U=(1,2), or d=(1,-1) and have k hills (a hill is either a ud or a Udd starting at the x-axis).

Table of values

List of values