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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 5040 |
| 8 | 40320 |
| 9 | 362880 |
| 10 | 362880 |
| 11 | 3991680 |
| 12 | 83825280 |
| 13 | 2598583680 |
| 14 | 106541930880 |
| 15 | 5433638474880 |
| 16 | 331451946967680 |
| 17 | 23533088234705280 |
| 18 | 1906180147011127680 |
| 19 | 173462393378012618880 |
[1,1,2,6,24,120,720,5040,40320,362880,362880, 3991680,83825280,2598583680,106541930880, 5433638474880,331451946967680,23533088234705280, 1906180147011127680,173462393378012618880] |