A137842 - cp's OEIS frontend

A137842 Number of paths from (0,0) if n is even, or from (2,1) if n is odd, to (3n,0) that stay in first quadrant (but may touch horizontal axis) and where each step is (2,1), (1,2) or (1,-1).

n	a(n)
0	1
1	1
2	2
3	4
4	10
5	24
6	66
7	172
8	498
9	1360
10	4066
11	11444
12	34970
13	100520
14	312066
15	911068
16	2862562
17	8457504
18	26824386
19	80006116
20	255680170
21	768464312
22	2471150402
23	7474561164
24	24161357010
25	73473471344
26	238552980386
27	728745517972

[1, 1, 2, 4, 10, 24, 66, 172, 498, 1360, 4066, 11444, 34970, 100520, 312066, 911068, 2862562, 8457504, 26824386, 80006116, 255680170, 768464312, 2471150402, 7474561164, 24161357010, 73473471344, 238552980386, 728745517972]

cp's OEIS Frontend

A137842 Number of paths from (0,0) if n is even, or from (2,1) if n is odd, to (3n,0) that stay in first quadrant (but may touch horizontal axis) and where each step is (2,1), (1,2) or (1,-1).

Table of values

List of values