| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 6 |
| 2 | 30 |
| 3 | 150 |
| 4 | 870 |
| 5 | 5070 |
| 6 | 30270 |
| 7 | 180750 |
| 8 | 1083630 |
| 9 | 6496710 |
| 10 | 38975190 |
| 11 | 233820870 |
| 12 | 1402894950 |
| 13 | 8417188950 |
| 14 | 50502952950 |
| 15 | 303016634070 |
| 16 | 1818098720790 |
| 17 | 10908585828030 |
| 18 | 65451508471470 |
| 19 | 392709011853630 |
| 20 | 2356254032146590 |
| 21 | 14137523959058670 |
| 22 | 84825143520531150 |
[0,6,30,150,870,5070,30270,180750,1083630,6496710, 38975190,233820870,1402894950,8417188950, 50502952950,303016634070,1818098720790, 10908585828030,65451508471470,392709011853630, 2356254032146590,14137523959058670, 84825143520531150] |