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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 63 |
| 3 | 2288 |
| 4 | 151200 |
| 5 | 15909696 |
| 6 | 2447297356 |
| 7 | 518678754048 |
| 8 | 145022370451200 |
| 9 | 51747613910720000 |
| 10 | 22956761806169786496 |
| 11 | 12397159038346976323584 |
| 12 | 8008689946841913447559168 |
| 13 | 6099405371286264105062400000 |
| 14 | 5408896545253926024119820000000 |
[1,4,63,2288,151200,15909696,2447297356, 518678754048,145022370451200,51747613910720000, 22956761806169786496,12397159038346976323584, 8008689946841913447559168, 6099405371286264105062400000, 5408896545253926024119820000000] |