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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 30 |
| 5 | 156 |
| 6 | 1455 |
| 7 | 11300 |
| 8 | 151221 |
| 9 | 1694723 |
| 10 | 29594446 |
| 11 | 404126228 |
| 12 | 10594925360 |
| 13 | 175238308453 |
| 14 | 5651774693595 |
| 15 | 117053117995400 |
| 16 | 5320744503742316 |
| 17 | 125889331236297288 |
| 18 | 7598016157515302757 |
[1,1,2,6,30,156,1455,11300,151221,1694723, 29594446,404126228,10594925360,175238308453, 5651774693595,117053117995400,5320744503742316, 125889331236297288,7598016157515302757] |