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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 20 |
| 3 | 312 |
| 4 | 9744 |
| 5 | 29280 |
| 6 | 53352 |
| 7 | 1666224 |
| 8 | 5006880 |
| 9 | 106798080 |
| 10 | 133301760 |
| 11 | 980733600 |
| 12 | 9099742080 |
| 13 | 18262471680 |
| 14 | 22794600960 |
| 15 | 1556055895680 |
| 16 | 3577201689600 |
| 17 | 4464942451200 |
| 18 | 380428773854896765462278360268800000 |
[1,20,312,9744,29280,53352,1666224,5006880, 106798080,133301760,980733600,9099742080, 18262471680,22794600960,1556055895680, 3577201689600,4464942451200, 380428773854896765462278360268800000] |