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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 40 |
| 5 | 360 |
| 6 | 4576 |
| 7 | 82656 |
| 8 | 2122240 |
| 9 | 77366400 |
| 10 | 4002843136 |
| 11 | 293717546496 |
| 12 | 30558458490880 |
| 13 | 4505780560619520 |
| 14 | 941417163728674816 |
| 15 | 278628902101315608576 |
| 16 | 116805328001281573519360 |
[0,1,6,40,360,4576,82656,2122240,77366400, 4002843136,293717546496,30558458490880, 4505780560619520,941417163728674816, 278628902101315608576,116805328001281573519360] |