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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 10 |
| 3 | 54 |
| 4 | 324 |
| 5 | 2130 |
| 6 | 15102 |
| 7 | 114282 |
| 8 | 915016 |
| 9 | 7701570 |
| 10 | 67785410 |
| 11 | 621241302 |
| 12 | 5907779100 |
| 13 | 58122866490 |
| 14 | 590120962494 |
| 15 | 6169755680850 |
| 16 | 66300171884560 |
| 17 | 731081377197218 |
| 18 | 8260198332989274 |
| 19 | 95504954267579062 |
[1,2,10,54,324,2130,15102,114282,915016,7701570, 67785410,621241302,5907779100,58122866490, 590120962494,6169755680850,66300171884560, 731081377197218,8260198332989274, 95504954267579062] |