n | a(n) |
---|---|
0 | 1 |
1 | 1 |
2 | 2 |
3 | 4 |
4 | 9 |
5 | 21 |
6 | 56 |
7 | 153 |
8 | 451 |
9 | 1357 |
10 | 4212 |
11 | 13308 |
12 | 42898 |
13 | 140276 |
14 | 465324 |
15 | 1561955 |
16 | 5300285 |
17 | 18156813 |
18 | 62732842 |
19 | 218405402 |
20 | 765657940 |
[1,1,2,4,9,21,56,153,451,1357,4212,13308,42898, 140276,465324,1561955,5300285,18156813,62732842, 218405402,765657940] |