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| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 281 |
| 3 | 2403 |
| 4 | 17929 |
| 5 | 132119 |
| 6 | 984595 |
| 7 | 7400832 |
| 8 | 55978489 |
| 9 | 425257387 |
| 10 | 3240026429 |
| 11 | 24732295031 |
| 12 | 189012200658 |
| 13 | 1445524081573 |
| 14 | 11059812977060 |
| 15 | 84641528773971 |
| 16 | 647871404690124 |
| 17 | 4959498660501284 |
| 18 | 37967742496830194 |
| 19 | 290676685330836460 |
[21,281,2403,17929,132119,984595,7400832,55978489, 425257387,3240026429,24732295031,189012200658, 1445524081573,11059812977060,84641528773971, 647871404690124,4959498660501284, 37967742496830194,290676685330836460] |