| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 39 |
| 5 | 174 |
| 6 | 858 |
| 7 | 4564 |
| 8 | 25793 |
| 9 | 153301 |
| 10 | 951325 |
| 11 | 6130757 |
| 12 | 40861658 |
| 13 | 280767621 |
| 14 | 1983859580 |
| 15 | 14385651988 |
| 16 | 106878699675 |
| 17 | 812480791324 |
| 18 | 6312686006725 |
| 19 | 50083418434737 |
| 20 | 405430892640225 |
| 21 | 3346568909331984 |
[1,1,3,10,39,174,858,4564,25793,153301,951325, 6130757,40861658,280767621,1983859580,14385651988, 106878699675,812480791324,6312686006725, 50083418434737,405430892640225,3346568909331984] |