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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 16 |
| 3 | 80 |
| 4 | 480 |
| 5 | 3840 |
| 6 | 42240 |
| 7 | 675840 |
| 8 | 16220160 |
| 9 | 600145920 |
| 10 | 34808463360 |
| 11 | 3202378629120 |
| 12 | 470749658480640 |
| 13 | 111096919401431040 |
| 14 | 42216829372543795200 |
| 15 | 25878916405369346457600 |
| 16 | 25620127241315652993024000 |
| 17 | 40992203586105044788838400000 |
[1,4,16,80,480,3840,42240,675840,16220160, 600145920,34808463360,3202378629120, 470749658480640,111096919401431040, 42216829372543795200,25878916405369346457600, 25620127241315652993024000, 40992203586105044788838400000] |