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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 3 |
| 3 | 20 |
| 4 | 231 |
| 5 | 3864 |
| 6 | 85140 |
| 7 | 2332616 |
| 8 | 76485227 |
| 9 | 2921536088 |
| 10 | 127421864328 |
| 11 | 6248486040840 |
| 12 | 340321635330534 |
| 13 | 20383240346962440 |
| 14 | 1331538898625750100 |
| 15 | 94216429100347571448 |
| 16 | 7178425650032302557691 |
| 17 | 585936966156456139931584 |
| 18 | 51011156414845408925712816 |
[1,3,20,231,3864,85140,2332616,76485227, 2921536088,127421864328,6248486040840, 340321635330534,20383240346962440, 1331538898625750100,94216429100347571448, 7178425650032302557691,585936966156456139931584, 51011156414845408925712816] |