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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 6 |
| 3 | 16 |
| 4 | 63 |
| 5 | 351 |
| 6 | 2609 |
| 7 | 24636 |
| 8 | 284631 |
| 9 | 3909926 |
| 10 | 62459868 |
| 11 | 1140206571 |
| 12 | 23453446130 |
| 13 | 537365482536 |
| 14 | 13583603874930 |
| 15 | 375783149051267 |
| 16 | 11299149697288503 |
| 17 | 367080116280553305 |
| 18 | 12818485840320445236 |
[1,3,6,16,63,351,2609,24636,284631,3909926, 62459868,1140206571,23453446130,537365482536, 13583603874930,375783149051267,11299149697288503, 367080116280553305,12818485840320445236] |