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| n | a(n) |
|---|---|
| 1 | 3 |
| 2 | 24 |
| 3 | 221 |
| 4 | 1922 |
| 5 | 15511 |
| 6 | 118857 |
| 7 | 876704 |
| 8 | 6281773 |
| 9 | 43997218 |
| 10 | 302544617 |
| 11 | 2049122034 |
| 12 | 13702872583 |
| 13 | 90643155972 |
| 14 | 593994248709 |
| 15 | 3860755349595 |
| 16 | 24913212937078 |
| 17 | 159737403339158 |
| 18 | 1018352525988640 |
| 19 | 6458838814490585 |
| 20 | 40774568909571868 |
[3,24,221,1922,15511,118857,876704,6281773, 43997218,302544617,2049122034,13702872583, 90643155972,593994248709,3860755349595, 24913212937078,159737403339158,1018352525988640, 6458838814490585,40774568909571868] |