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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 7 |
| 5 | 30 |
| 6 | 163 |
| 7 | 1056 |
| 8 | 7919 |
| 9 | 67304 |
| 10 | 639384 |
| 11 | 6713531 |
| 12 | 77205602 |
| 13 | 965070018 |
| 14 | 13028445232 |
| 15 | 188912455861 |
| 16 | 2928143065835 |
| 17 | 48314360586265 |
| 18 | 845501310259628 |
| 19 | 15641774239803108 |
| 20 | 305014597676160594 |
| 21 | 6252799252361292174 |
[1,1,1,2,7,30,163,1056,7919,67304,639384,6713531, 77205602,965070018,13028445232,188912455861, 2928143065835,48314360586265,845501310259628, 15641774239803108,305014597676160594, 6252799252361292174] |