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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 0 |
| 8 | 1 |
| 9 | 3 |
| 10 | 12 |
| 11 | 60 |
| 12 | 357 |
| 13 | 2508 |
| 14 | 20100 |
| 15 | 181080 |
| 16 | 1811886 |
| 17 | 19938270 |
| 18 | 239319540 |
| 19 | 3111697260 |
| 20 | 43569197270 |
| 21 | 653597773860 |
| 22 | 10458282340380 |
| 23 | 177800134878240 |
| 24 | 3200533135400175 |
| 25 | 60812090365924905 |
| 26 | 1216273182165519240 |
| 27 | 25542270225880538760 |
[0,0,0,0,0,0,0,0,1,3,12,60,357,2508,20100,181080, 1811886,19938270,239319540,3111697260,43569197270, 653597773860,10458282340380,177800134878240, 3200533135400175,60812090365924905, 1216273182165519240,25542270225880538760] |