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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 17 |
| 5 | 50 |
| 6 | 163 |
| 7 | 525 |
| 8 | 1770 |
| 9 | 6066 |
| 10 | 21154 |
| 11 | 74787 |
| 12 | 267371 |
| 13 | 965233 |
| 14 | 3513029 |
| 15 | 12877687 |
| 16 | 47499333 |
| 17 | 176167086 |
| 18 | 656568385 |
| 19 | 2457710598 |
| 20 | 9236079055 |
| 21 | 34832753818 |
| 22 | 131792634266 |
| 23 | 500121476517 |
| 24 | 1902979982421 |
| 25 | 7258942377746 |
| 26 | 27752992782498 |
| 27 | 106333425162358 |
| 28 | 408213503595652 |
[1,1,2,6,17,50,163,525,1770,6066,21154,74787, 267371,965233,3513029,12877687,47499333,176167086, 656568385,2457710598,9236079055,34832753818, 131792634266,500121476517,1902979982421, 7258942377746,27752992782498,106333425162358, 408213503595652] |