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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 9 |
| 4 | 52 |
| 5 | 355 |
| 6 | 2976 |
| 7 | 29897 |
| 8 | 343988 |
| 9 | 4423503 |
| 10 | 63088600 |
| 11 | 992691205 |
| 12 | 17095554444 |
| 13 | 319404545291 |
| 14 | 6427307831504 |
| 15 | 138546745515393 |
| 16 | 3185841858310180 |
| 17 | 77866726065935239 |
| 18 | 2016161715005701128 |
| 19 | 55127056896177521981 |
| 20 | 1587073087715010466556 |
| 21 | 47982707153606476112067 |
| 22 | 1519931218769637781731712 |
[1,1,2,9,52,355,2976,29897,343988,4423503, 63088600,992691205,17095554444,319404545291, 6427307831504,138546745515393,3185841858310180, 77866726065935239,2016161715005701128, 55127056896177521981,1587073087715010466556, 47982707153606476112067,1519931218769637781731712] |