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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 9 |
| 3 | 39 |
| 4 | 168 |
| 5 | 723 |
| 6 | 3111 |
| 7 | 13386 |
| 8 | 57597 |
| 9 | 247827 |
| 10 | 1066344 |
| 11 | 4588239 |
| 12 | 19742163 |
| 13 | 84946098 |
| 14 | 365504001 |
| 15 | 1572681711 |
| 16 | 6766896552 |
| 17 | 29116437627 |
| 18 | 125281498479 |
| 19 | 539058179514 |
| 20 | 2319446402133 |
| 21 | 9980057472123 |
| 22 | 42941948154216 |
[1,2,9,39,168,723,3111,13386,57597,247827,1066344, 4588239,19742163,84946098,365504001,1572681711, 6766896552,29116437627,125281498479,539058179514, 2319446402133,9980057472123,42941948154216] |