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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 45 |
| 3 | 816 |
| 4 | 20475 |
| 5 | 658008 |
| 6 | 25827165 |
| 7 | 1198774720 |
| 8 | 64276915527 |
| 9 | 3911395881900 |
| 10 | 266401260897200 |
| 11 | 20082459351180240 |
| 12 | 1660305826125766950 |
| 13 | 149389005978091284720 |
| 14 | 14533945899753270066525 |
| 15 | 1520398315196482557890304 |
| 16 | 170190601112537814791748255 |
[1,4,45,816,20475,658008,25827165,1198774720, 64276915527,3911395881900,266401260897200, 20082459351180240,1660305826125766950, 149389005978091284720,14533945899753270066525, 1520398315196482557890304, 170190601112537814791748255] |