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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 80 |
| 6 | 326 |
| 7 | 1566 |
| 8 | 9544 |
| 9 | 65036 |
| 10 | 518498 |
| 11 | 4750006 |
| 12 | 48830634 |
| 13 | 554929274 |
| 14 | 6926227324 |
| 15 | 93970452970 |
| 16 | 1377573324202 |
[1,1,2,6,24,80,326,1566,9544,65036,518498,4750006, 48830634,554929274,6926227324,93970452970, 1377573324202] |