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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 20 |
| 4 | 82 |
| 5 | 435 |
| 6 | 2645 |
| 7 | 18489 |
| 8 | 141326 |
| 9 | 1153052 |
| 10 | 9819315 |
| 11 | 86305315 |
| 12 | 776868505 |
[1,2,5,20,82,435,2645,18489,141326,1153052, 9819315,86305315,776868505] |