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| n | a(n) |
|---|---|
| 1 | 6 |
| 2 | 152 |
| 3 | 1608 |
| 4 | 15420 |
| 5 | 127980 |
| 6 | 1003360 |
| 7 | 7432708 |
| 8 | 53294540 |
| 9 | 371397240 |
| 10 | 2537155684 |
| 11 | 17047659916 |
| 12 | 113102692016 |
| 13 | 742597784164 |
| 14 | 4835184613212 |
| 15 | 31267479066856 |
| 16 | 201066698078244 |
| 17 | 1286998671857356 |
| 18 | 8206523391863296 |
[6,152,1608,15420,127980,1003360,7432708,53294540, 371397240,2537155684,17047659916,113102692016, 742597784164,4835184613212,31267479066856, 201066698078244,1286998671857356,8206523391863296] |