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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 10 |
| 4 | 46 |
| 5 | 252 |
| 6 | 1642 |
| 7 | 12316 |
| 8 | 104730 |
| 9 | 995122 |
| 10 | 10450414 |
| 11 | 120192924 |
| 12 | 1502537932 |
| 13 | 20285580880 |
| 14 | 294156077364 |
| 15 | 4559608340968 |
| 16 | 75236088623548 |
| 17 | 1316668510772124 |
| 18 | 24358939966126900 |
| 19 | 475008770990906488 |
| 20 | 9737844963832507656 |
| 21 | 209366721066736679536 |
[1,1,3,10,46,252,1642,12316,104730,995122, 10450414,120192924,1502537932,20285580880, 294156077364,4559608340968,75236088623548, 1316668510772124,24358939966126900, 475008770990906488,9737844963832507656, 209366721066736679536] |