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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 1 |
| 5 | 10 |
| 6 | 85 |
| 7 | 735 |
| 8 | 6839 |
| 9 | 69804 |
| 10 | 784580 |
| 11 | 9680000 |
| 12 | 130312336 |
| 13 | 1901581968 |
| 14 | 29895585356 |
| 15 | 503657235900 |
| 16 | 9051009737834 |
| 17 | 172807817059664 |
| 18 | 3493189152511608 |
| 19 | 74530548004474584 |
| 20 | 1673793045085649146 |
| 21 | 39467836062718058100 |
| 22 | 974939402596817961050 |
| 23 | 25177327470510057799550 |
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