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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 108 |
| 4 | 4448 |
| 5 | 276560 |
| 6 | 24034752 |
| 7 | 2782112704 |
| 8 | 413640580096 |
| 9 | 76768625740032 |
| 10 | 17380983003345920 |
| 11 | 4711153236657376256 |
| 12 | 1505098422997799215104 |
| 13 | 559357234754573189828608 |
[0,1,4,108,4448,276560,24034752,2782112704, 413640580096,76768625740032,17380983003345920, 4711153236657376256,1505098422997799215104, 559357234754573189828608] |