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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 18 |
| 3 | 96 |
| 4 | 560 |
| 5 | 720 |
| 6 | 1056 |
| 7 | 1760 |
| 8 | 2000 |
| 9 | 3264 |
| 10 | 7392 |
| 11 | 30960 |
| 12 | 50800 |
| 13 | 172080 |
| 14 | 173440 |
| 15 | 9561600 |
| 16 | 13304064 |
| 17 | 195522560 |
| 18 | 1017856448 |
| 19 | 1026021024 |
| 20 | 1568010240 |
| 21 | 2817884160 |
[1,18,96,560,720,1056,1760,2000,3264,7392,30960, 50800,172080,173440,9561600,13304064,195522560, 1017856448,1026021024,1568010240,2817884160] |