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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 19 |
| 3 | 117 |
| 4 | 721 |
| 5 | 4443 |
| 6 | 27379 |
| 7 | 168717 |
| 8 | 1039681 |
| 9 | 6406803 |
| 10 | 39480499 |
| 11 | 243289797 |
[1,3,19,117,721,4443,27379,168717,1039681,6406803, 39480499,243289797] |