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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 9 |
| 2 | 45 |
| 3 | 165 |
| 4 | 495 |
| 5 | 1287 |
| 6 | 3003 |
| 7 | 6435 |
| 8 | 12869 |
| 9 | 24301 |
| 10 | 43713 |
| 11 | 75417 |
| 12 | 125475 |
| 13 | 202203 |
| 14 | 316767 |
| 15 | 483879 |
| 16 | 722601 |
| 17 | 1057265 |
| 18 | 1518517 |
| 19 | 2144493 |
| 20 | 2982135 |
| 21 | 4088655 |
| 22 | 5533155 |
| 23 | 7398411 |
| 24 | 9782829 |
| 25 | 12802581 |
| 26 | 16593929 |
[1,9,45,165,495,1287,3003,6435,12869,24301,43713, 75417,125475,202203,316767,483879,722601,1057265, 1518517,2144493,2982135,4088655,5533155,7398411, 9782829,12802581,16593929] |