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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 4 |
| 5 | 22 |
| 6 | 125 |
| 7 | 809 |
| 8 | 5929 |
| 9 | 48336 |
| 10 | 443762 |
| 11 | 4469217 |
| 12 | 49647760 |
| 13 | 597806704 |
| 14 | 7809581207 |
| 15 | 109524955614 |
[0,0,1,4,22,125,809,5929,48336,443762,4469217, 49647760,597806704,7809581207,109524955614] |