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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 36 |
| 4 | 576 |
| 5 | 72000 |
| 6 | 15552000 |
| 7 | 5334336000 |
| 8 | 2731180032000 |
| 9 | 1991030243328000 |
| 10 | 19910302433280000000 |
| 11 | 291506737925652480000000 |
| 12 | 6044683717626329825280000000 |
| 13 | 172642211659125606139822080000000 |
| 14 | 6632223203096969285467405025280000000 |
| 15 | 335756299656784070076787379404800000000000 |
[1,1,4,36,576,72000,15552000,5334336000, 2731180032000,1991030243328000, 19910302433280000000,291506737925652480000000, 6044683717626329825280000000, 172642211659125606139822080000000, 6632223203096969285467405025280000000, 335756299656784070076787379404800000000000] |