A108449 - cp's OEIS frontend

A108449 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 having no pyramids (a pyramid is a sequence u^pd^p or U^pd^(2p) for some positive integer p, starting at the x-axis).

n	a(n)
0	1
1	0
2	4
3	32
4	252
5	2112
6	18484
7	166976
8	1545548
9	14583808
10	139774180
11	1356966240
12	13316740764
13	131890671680
14	1316627340564
15	13234192747648
16	133829733962732
17	1360586260341248
18	13898403178004420
19	142578916276009632

[1, 0, 4, 32, 252, 2112, 18484, 166976, 1545548, 14583808, 139774180, 1356966240, 13316740764, 131890671680, 1316627340564, 13234192747648, 133829733962732, 1360586260341248, 13898403178004420, 142578916276009632]

cp's OEIS Frontend

A108449 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 having no pyramids (a pyramid is a sequence u^pd^p or U^pd^(2p) for some positive integer p, starting at the x-axis).

Table of values

List of values