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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 24 |
| 5 | 121 |
| 6 | 840 |
| 7 | 5041 |
| 8 | 40320 |
| 9 | 423361 |
| 10 | 3659040 |
| 11 | 39916801 |
| 12 | 558835200 |
| 13 | 6227020801 |
| 14 | 87195588480 |
| 15 | 1536517382401 |
| 16 | 20922789888000 |
| 17 | 355687428096001 |
| 18 | 7469453633241600 |
| 19 | 121645100408832001 |
| 20 | 2453176191578112000 |
| 21 | 59616236292028416001 |
[1,2,7,24,121,840,5041,40320,423361,3659040, 39916801,558835200,6227020801,87195588480, 1536517382401,20922789888000,355687428096001, 7469453633241600,121645100408832001, 2453176191578112000,59616236292028416001] |