| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 3 |
| 5 | 8 |
| 6 | 27 |
| 7 | 96 |
| 8 | 569 |
| 9 | 4093 |
| 10 | 37611 |
| 11 | 421080 |
| 12 | 6366190 |
| 13 | 123605120 |
| 14 | 3088656877 |
| 15 | 98116765714 |
| 16 | 4039581343182 |
| 17 | 214357411746908 |
| 18 | 14651947137883915 |
| 19 | 1285925403332066988 |
| 20 | 145385760960996273023 |
| 21 | 21168918836708595100735 |
[1,1,1,3,8,27,96,569,4093,37611,421080,6366190, 123605120,3088656877,98116765714,4039581343182, 214357411746908,14651947137883915, 1285925403332066988,145385760960996273023, 21168918836708595100735] |