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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 24 |
| 4 | 431 |
| 5 | 7155 |
| 6 | 117454 |
| 7 | 1961470 |
| 8 | 33775244 |
| 9 | 603682596 |
| 10 | 11235811536 |
| 11 | 218055250512 |
| 12 | 4413843664416 |
| 13 | 93156324734304 |
| 14 | 2048591287486080 |
| 15 | 46898664421553280 |
| 16 | 1116592842912341760 |
| 17 | 27618683992928743680 |
[0,0,1,24,431,7155,117454,1961470,33775244, 603682596,11235811536,218055250512,4413843664416, 93156324734304,2048591287486080,46898664421553280, 1116592842912341760,27618683992928743680] |