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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 10 |
| 3 | 70 |
| 4 | 550 |
| 5 | 4590 |
| 6 | 39774 |
| 7 | 353860 |
| 8 | 3210940 |
| 9 | 29581000 |
| 10 | 275808700 |
| 11 | 2596707296 |
[2,10,70,550,4590,39774,353860,3210940,29581000, 275808700,2596707296] |