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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 13 |
| 4 | 56 |
| 5 | 1109 |
| 6 | 43480 |
| 7 | 2525039 |
| 8 | 351431316 |
| 9 | 112149224917 |
| 10 | 58115173076989 |
[1,4,13,56,1109,43480,2525039,351431316, 112149224917,58115173076989] |