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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 68 |
| 5 | 760 |
| 6 | 11664 |
| 7 | 233828 |
| 8 | 5905696 |
| 9 | 182846592 |
| 10 | 6792372480 |
| 11 | 297550188672 |
| 12 | 15153482847744 |
| 13 | 886517886778368 |
| 14 | 58975120009537536 |
| 15 | 4422337095720648960 |
| 16 | 370957479138591903744 |
| 17 | 34576037926690499493888 |
| 18 | 3559813114275891217760256 |
[1,2,9,68,760,11664,233828,5905696,182846592, 6792372480,297550188672,15153482847744, 886517886778368,58975120009537536, 4422337095720648960,370957479138591903744, 34576037926690499493888,3559813114275891217760256] |