A226995 - cp's OEIS frontend

A226995 Number of lattice paths from (0,0) to (n,n) consisting of steps U=(1,1), H=(1,0) and S=(0,1) such that the first step leaving the diagonal (if any) is an H step and the last step joining the diagonal (if any) is a S step.

n	a(n)
0	1
1	2
2	6
3	23
4	103
5	504
6	2588
7	13661
8	73373
9	398814
10	2186818
11	12072275
12	67004451
13	373532596
14	2089994360
15	11730304377
16	66012996217
17	372350924666
18	2104523577534
19	11916013288271
20	67576932913951
21	383781666337072
22	2182362613988116
23	12424357722805333

[1, 2, 6, 23, 103, 504, 2588, 13661, 73373, 398814, 2186818, 12072275, 67004451, 373532596, 2089994360, 11730304377, 66012996217, 372350924666, 2104523577534, 11916013288271, 67576932913951, 383781666337072, 2182362613988116, 12424357722805333]

cp's OEIS Frontend

A226995 Number of lattice paths from (0,0) to (n,n) consisting of steps U=(1,1), H=(1,0) and S=(0,1) such that the first step leaving the diagonal (if any) is an H step and the last step joining the diagonal (if any) is a S step.

Table of values

List of values