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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 8 |
| 4 | 15 |
| 5 | 624 |
| 6 | 35 |
| 7 | 117648 |
| 8 | 4095 |
| 9 | 531440 |
| 10 | 9999 |
| 11 | 25937424600 |
| 12 | 20735 |
| 13 | 23298085122480 |
| 14 | 7529535 |
| 15 | 2562890624 |
| 16 | 4294967295 |
| 17 | 48661191875666868480 |
| 18 | 34012223 |
| 19 | 104127350297911241532840 |
| 20 | 25599999999 |
| 21 | 7355827511386640 |
[0,1,8,15,624,35,117648,4095,531440,9999, 25937424600,20735,23298085122480,7529535, 2562890624,4294967295,48661191875666868480, 34012223,104127350297911241532840,25599999999, 7355827511386640] |