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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 21 |
| 6 | 45 |
| 7 | 121 |
| 8 | 261 |
| 9 | 723 |
| 10 | 1723 |
| 11 | 5087 |
| 12 | 13091 |
| 13 | 38641 |
| 14 | 101993 |
| 15 | 297423 |
| 16 | 800187 |
| 17 | 2324961 |
| 18 | 6378601 |
| 19 | 18544345 |
| 20 | 51670725 |
| 21 | 150172263 |
| 22 | 422922591 |
| 23 | 1228542913 |
| 24 | 3488055573 |
| 25 | 10134018375 |
| 26 | 28962183951 |
| 27 | 84203226523 |
| 28 | 241924870591 |
[1,1,3,7,21,45,121,261,723,1723,5087,13091,38641, 101993,297423,800187,2324961,6378601,18544345, 51670725,150172263,422922591,1228542913, 3488055573,10134018375,28962183951,84203226523, 241924870591] |