A108424 - cp's OEIS frontend

A108424 Number of paths from (0,0) to (3n,0) that stay in the first quadrant, consist of steps u=(2,1), U=(1,2), or d=(1,-1) and do not touch the x-axis, except at the endpoints.

n	a(n)
1	2
2	6
3	34
4	238
5	1858
6	15510
7	135490
8	1223134
9	11320066
10	106830502
11	1024144482
12	9945711566
13	97634828354
14	967298498358
15	9659274283650
16	97119829841854
17	982391779220482
18	9990160542904134
19	102074758837531810
20	1047391288012377774
21	10788532748880319298

[2, 6, 34, 238, 1858, 15510, 135490, 1223134, 11320066, 106830502, 1024144482, 9945711566, 97634828354, 967298498358, 9659274283650, 97119829841854, 982391779220482, 9990160542904134, 102074758837531810, 1047391288012377774, 10788532748880319298]

cp's OEIS Frontend

A108424 Number of paths from (0,0) to (3n,0) that stay in the first quadrant, consist of steps u=(2,1), U=(1,2), or d=(1,-1) and do not touch the x-axis, except at the endpoints.

Table of values

List of values