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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 60 |
| 4 | 420 |
| 5 | 4620 |
| 6 | 60060 |
| 7 | 4084080 |
| 8 | 232792560 |
| 9 | 5354228880 |
| 10 | 155272637520 |
| 11 | 4813451763120 |
| 12 | 178097715235440 |
| 13 | 7302006324653040 |
| 14 | 313986271960080720 |
| 15 | 14757354782123793840 |
| 16 | 782139803452561073520 |
| 17 | 46146248403701103337680 |
| 18 | 2814921152625767303598480 |
[1,2,6,60,420,4620,60060,4084080,232792560, 5354228880,155272637520,4813451763120, 178097715235440,7302006324653040, 313986271960080720,14757354782123793840, 782139803452561073520,46146248403701103337680, 2814921152625767303598480] |