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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 144 |
| 3 | 576 |
| 4 | 518400 |
| 5 | 2073600 |
| 6 | 3657830400 |
| 7 | 696729600 |
| 8 | 13168189440000 |
| 9 | 52672757760000 |
| 10 | 45888506560512000 |
| 11 | 917770131210240000 |
| 12 | 6840049010896797696000000 |
| 13 | 1013340594206932992000000 |
| 14 | 984967057569138868224000000 |
| 15 | 562838318610936496128000000 |
[1,4,144,576,518400,2073600,3657830400,696729600, 13168189440000,52672757760000,45888506560512000, 917770131210240000,6840049010896797696000000, 1013340594206932992000000, 984967057569138868224000000, 562838318610936496128000000] |