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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 3 |
| 4 | 12 |
| 5 | 56 |
| 6 | 321 |
| 7 | 2175 |
| 8 | 17008 |
| 9 | 150504 |
| 10 | 1485465 |
| 11 | 16170035 |
| 12 | 192384876 |
| 13 | 2483177808 |
| 14 | 34554278857 |
| 15 | 515620794591 |
| 16 | 8212685046336 |
| 17 | 139062777326000 |
| 18 | 2494364438359953 |
| 19 | 47245095998005059 |
| 20 | 942259727190907180 |
| 21 | 19737566982241851720 |
| 22 | 433234326593362631601 |
| 23 | 9943659797649140568863 |
[1,3,12,56,321,2175,17008,150504,1485465,16170035, 192384876,2483177808,34554278857,515620794591, 8212685046336,139062777326000,2494364438359953, 47245095998005059,942259727190907180, 19737566982241851720,433234326593362631601, 9943659797649140568863] |