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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 135 |
| 4 | 1053 |
| 5 | 8505 |
| 6 | 70470 |
| 7 | 594135 |
| 8 | 5073840 |
| 9 | 43761870 |
| 10 | 380433024 |
| 11 | 3328474032 |
| 12 | 29276671347 |
| 13 | 258669163665 |
| 14 | 2294194659012 |
| 15 | 20415148177023 |
| 16 | 182191712018409 |
| 17 | 1630078264917999 |
| 18 | 14617308518871210 |
| 19 | 131341152706852599 |
[1,3,18,135,1053,8505,70470,594135,5073840, 43761870,380433024,3328474032,29276671347, 258669163665,2294194659012,20415148177023, 182191712018409,1630078264917999, 14617308518871210,131341152706852599] |