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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 120 |
| 6 | 720 |
| 7 | 4320 |
| 8 | 25920 |
| 9 | 155520 |
| 10 | 933120 |
| 11 | 5223720 |
| 12 | 28065624 |
| 13 | 148043310 |
| 14 | 779305142 |
| 15 | 4138663683 |
| 16 | 22326100565 |
| 17 | 121438789028 |
| 18 | 662769584476 |
| 19 | 3618469944096 |
| 20 | 19732129903872 |
| 21 | 107425688617728 |
| 22 | 584061299353728 |
[1,2,6,24,120,720,4320,25920,155520,933120, 5223720,28065624,148043310,779305142,4138663683, 22326100565,121438789028,662769584476, 3618469944096,19732129903872,107425688617728, 584061299353728] |