| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 48 |
| 4 | 249 |
| 5 | 1240 |
| 6 | 5992 |
| 7 | 28369 |
| 8 | 132427 |
| 9 | 611901 |
| 10 | 2805670 |
| 11 | 12786249 |
| 12 | 57979474 |
| 13 | 261797013 |
| 14 | 1177774158 |
| 15 | 5281497918 |
[1,2,9,48,249,1240,5992,28369,132427,611901, 2805670,12786249,57979474,261797013,1177774158, 5281497918] |