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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 7 |
| 3 | 57 |
| 4 | 455 |
| 5 | 3641 |
| 6 | 29127 |
| 7 | 233017 |
| 8 | 1864135 |
| 9 | 14913081 |
| 10 | 119304647 |
| 11 | 954437177 |
[0,1,7,57,455,3641,29127,233017,1864135,14913081, 119304647,954437177] |