| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 8 |
| 3 | 58 |
| 4 | 432 |
| 5 | 3396 |
| 6 | 28384 |
| 7 | 252456 |
| 8 | 2385280 |
| 9 | 23874448 |
| 10 | 252380800 |
| 11 | 2809461920 |
| 12 | 32841595136 |
| 13 | 402105388608 |
| 14 | 5144478074368 |
| 15 | 68625615724160 |
| 16 | 952603633463296 |
| 17 | 13735016459768064 |
| 18 | 205358227932235776 |
| 19 | 3179027634604907008 |
| 20 | 50881656554805620736 |
| 21 | 840901491722391454720 |
| 22 | 14332437167995507302400 |
[0,1,8,58,432,3396,28384,252456,2385280,23874448, 252380800,2809461920,32841595136,402105388608, 5144478074368,68625615724160,952603633463296, 13735016459768064,205358227932235776, 3179027634604907008,50881656554805620736, 840901491722391454720,14332437167995507302400] |