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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 9 |
| 4 | 96 |
| 5 | 1170 |
| 6 | 18324 |
| 7 | 340200 |
| 8 | 7360128 |
| 9 | 181476288 |
| 10 | 5024611440 |
| 11 | 154319988240 |
| 12 | 5206240427904 |
| 13 | 191372822989920 |
| 14 | 7612497915813504 |
| 15 | 325791049256094240 |
| 16 | 14925809593280332800 |
| 17 | 728828735500650355200 |
| 18 | 37786217117138333005824 |
[1,0,2,9,96,1170,18324,340200,7360128,181476288, 5024611440,154319988240,5206240427904, 191372822989920,7612497915813504, 325791049256094240,14925809593280332800, 728828735500650355200,37786217117138333005824] |