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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 37 |
| 5 | 260 |
| 6 | 2365 |
| 7 | 24850 |
| 8 | 301033 |
| 9 | 4051848 |
| 10 | 60901145 |
| 11 | 1003420638 |
| 12 | 18072389069 |
| 13 | 352027414284 |
| 14 | 7390186076949 |
| 15 | 166110699895530 |
| 16 | 3983896292586577 |
| 17 | 101488729722338064 |
| 18 | 2737830394817774257 |
[1,0,1,6,37,260,2365,24850,301033,4051848, 60901145,1003420638,18072389069,352027414284, 7390186076949,166110699895530,3983896292586577, 101488729722338064,2737830394817774257] |