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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 76 |
| 6 | 273 |
| 7 | 971 |
| 8 | 3439 |
| 9 | 12172 |
| 10 | 43098 |
| 11 | 152649 |
| 12 | 540730 |
| 13 | 1915445 |
| 14 | 6785029 |
| 15 | 24034177 |
| 16 | 85134498 |
| 17 | 301565746 |
| 18 | 1068215101 |
| 19 | 3783864272 |
| 20 | 13403320805 |
| 21 | 47477655647 |
| 22 | 168176809999 |
| 23 | 595721056436 |
| 24 | 2110181402286 |
| 25 | 7474749309041 |
[1,2,6,21,76,273,971,3439,12172,43098,152649, 540730,1915445,6785029,24034177,85134498, 301565746,1068215101,3783864272,13403320805, 47477655647,168176809999,595721056436, 2110181402286,7474749309041] |