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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 26 |
| 4 | 115 |
| 5 | 596 |
| 6 | 3331 |
| 7 | 19100 |
| 8 | 110329 |
| 9 | 638540 |
| 10 | 3697405 |
| 11 | 21411974 |
| 12 | 124001893 |
| 13 | 718129334 |
| 14 | 4158891979 |
| 15 | 24085338398 |
| 16 | 139485124807 |
| 17 | 807798504728 |
| 18 | 4678193659303 |
| 19 | 27092766081872 |
| 20 | 156902006957821 |
[1,2,7,26,115,596,3331,19100,110329,638540, 3697405,21411974,124001893,718129334,4158891979, 24085338398,139485124807,807798504728, 4678193659303,27092766081872,156902006957821] |