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| n | a(n) |
|---|---|
| 4 | 0 |
| 5 | 0 |
| 6 | 0 |
| 7 | 18 |
| 8 | 400 |
| 9 | 7850 |
| 10 | 162288 |
| 11 | 3667650 |
| 12 | 91171008 |
| 13 | 2486784402 |
| 14 | 74062575400 |
| 15 | 2395420006034 |
| 16 | 83695120256592 |
| 17 | 3143661612445146 |
| 18 | 126375169532421600 |
| 19 | 5415486851106043650 |
| 20 | 246486713303685957376 |
[0,0,0,18,400,7850,162288,3667650,91171008, 2486784402,74062575400,2395420006034, 83695120256592,3143661612445146, 126375169532421600,5415486851106043650, 246486713303685957376] |