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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 21 |
| 3 | 455 |
| 4 | 14950 |
| 5 | 658008 |
| 6 | 36288252 |
| 7 | 2404808340 |
| 8 | 186087894300 |
| 9 | 16466440817750 |
| 10 | 1639875152957965 |
| 11 | 181513211783531667 |
| 12 | 22105238818111121361 |
| 13 | 2937279723907795168000 |
| 14 | 422879027090638497044400 |
| 15 | 65572027180886570401929144 |
| 16 | 10894880155433107077641916792 |
[1,2,21,455,14950,658008,36288252,2404808340, 186087894300,16466440817750,1639875152957965, 181513211783531667,22105238818111121361, 2937279723907795168000,422879027090638497044400, 65572027180886570401929144, 10894880155433107077641916792] |