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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 28 |
| 2 | 1308 |
| 3 | 85632 |
| 4 | 7215504 |
| 5 | 743895360 |
| 6 | 90735698880 |
| 7 | 12784048058880 |
| 8 | 2043605420478720 |
| 9 | 365523503117552640 |
| 10 | 72341521311159475200 |
| 11 | 15698552277109576089600 |
| 12 | 3707121435080668435353600 |
[1,28,1308,85632,7215504,743895360,90735698880, 12784048058880,2043605420478720, 365523503117552640,72341521311159475200, 15698552277109576089600,3707121435080668435353600] |