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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 7 |
| 3 | 56 |
| 4 | 609 |
| 5 | 8960 |
| 6 | 162015 |
| 7 | 3455760 |
| 8 | 85499505 |
| 9 | 2407507200 |
| 10 | 75954495015 |
| 11 | 2654662651200 |
| 12 | 101833013541105 |
| 13 | 4253509461922560 |
| 14 | 192174397814079135 |
| 15 | 9338303873329240320 |
| 16 | 485654062232697912225 |
| 17 | 26915598265961374986240 |
| 18 | 1583628181230906140008455 |
[1,1,7,56,609,8960,162015,3455760,85499505, 2407507200,75954495015,2654662651200, 101833013541105,4253509461922560, 192174397814079135,9338303873329240320, 485654062232697912225,26915598265961374986240, 1583628181230906140008455] |