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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 23 |
| 5 | 103 |
| 6 | 516 |
| 7 | 2819 |
| 8 | 16517 |
| 9 | 102615 |
| 10 | 670503 |
| 11 | 4580064 |
| 12 | 32553887 |
| 13 | 239884108 |
| 14 | 1827188093 |
| 15 | 14351353937 |
| 16 | 115997378072 |
| 17 | 963164672275 |
| 18 | 8203632154685 |
| 19 | 71582150287243 |
| 20 | 639150768866594 |
| 21 | 5833969369906384 |
| 22 | 54387003936658041 |
| 23 | 517419092989229133 |
[1,1,2,6,23,103,516,2819,16517,102615,670503, 4580064,32553887,239884108,1827188093,14351353937, 115997378072,963164672275,8203632154685, 71582150287243,639150768866594,5833969369906384, 54387003936658041,517419092989229133] |