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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 12 |
| 5 | 20 |
| 6 | 360 |
| 7 | 2520 |
| 8 | 1680 |
| 9 | 15120 |
| 10 | 151200 |
| 11 | 554400 |
| 12 | 9979200 |
| 13 | 129729600 |
| 14 | 605404800 |
| 15 | 27243216000 |
| 16 | 54486432000 |
| 17 | 308756448000 |
| 18 | 5557616064000 |
| 19 | 8122669632000 |
| 20 | 351982350720000 |
| 21 | 22174888095360000 |
| 22 | 25676186215680000 |
| 23 | 3740164458750720000 |
| 24 | 67322960257512960000 |
[1,1,2,6,12,20,360,2520,1680,15120,151200,554400, 9979200,129729600,605404800,27243216000, 54486432000,308756448000,5557616064000, 8122669632000,351982350720000,22174888095360000, 25676186215680000,3740164458750720000, 67322960257512960000] |