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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 21 |
| 3 | 378 |
| 4 | 9819 |
| 5 | 338978 |
| 6 | 14802427 |
| 7 | 790660090 |
| 8 | 50405704473 |
| 9 | 3763429394138 |
| 10 | 324142520562853 |
| 11 | 31809195929392082 |
[1,2,21,378,9819,338978,14802427,790660090, 50405704473,3763429394138,324142520562853, 31809195929392082] |