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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 7 |
| 3 | 33 |
| 4 | 173 |
| 5 | 962 |
| 6 | 5586 |
| 7 | 33498 |
| 8 | 205846 |
| 9 | 1289386 |
| 10 | 8202247 |
| 11 | 52845855 |
| 12 | 344129832 |
| 13 | 2261377872 |
| 14 | 14976646685 |
| 15 | 99863119809 |
| 16 | 669860309538 |
| 17 | 4517037850220 |
| 18 | 30603008068997 |
| 19 | 208211448723097 |
| 20 | 1421986458302466 |
| 21 | 9745007758311114 |
| 22 | 66993247112160800 |
[1,2,7,33,173,962,5586,33498,205846,1289386, 8202247,52845855,344129832,2261377872,14976646685, 99863119809,669860309538,4517037850220, 30603008068997,208211448723097,1421986458302466, 9745007758311114,66993247112160800] |