| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 54 |
| 4 | 413 |
| 5 | 3161 |
| 6 | 24192 |
| 7 | 185149 |
| 8 | 1417003 |
| 9 | 10844766 |
| 10 | 82998377 |
| 11 | 635212469 |
| 12 | 4861479168 |
| 13 | 37206416521 |
| 14 | 284752311487 |
| 15 | 2179298263014 |
| 16 | 16678849398533 |
| 17 | 127648437104801 |
| 18 | 976933306726272 |
| 19 | 7476775332607909 |
| 20 | 57222093861886723 |
[0,1,7,54,413,3161,24192,185149,1417003,10844766, 82998377,635212469,4861479168,37206416521, 284752311487,2179298263014,16678849398533, 127648437104801,976933306726272,7476775332607909, 57222093861886723] |