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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 9 |
| 3 | 30 |
| 4 | 120 |
| 5 | 582 |
| 6 | 3351 |
| 7 | 22395 |
| 8 | 170505 |
| 9 | 1457238 |
| 10 | 13816869 |
| 11 | 143942445 |
| 12 | 1634497320 |
| 13 | 20093354217 |
| 14 | 265873928856 |
| 15 | 3767702766825 |
| 16 | 56931647539755 |
| 17 | 913761523938678 |
| 18 | 15524893940956074 |
| 19 | 278364926845016820 |
[1,3,9,30,120,582,3351,22395,170505,1457238, 13816869,143942445,1634497320,20093354217, 265873928856,3767702766825,56931647539755, 913761523938678,15524893940956074, 278364926845016820] |