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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 18 |
| 3 | 180 |
| 4 | 2670 |
| 5 | 54096 |
| 6 | 1411228 |
| 7 | 45421776 |
| 8 | 1747674405 |
| 9 | 78485504845 |
| 10 | 4037946005808 |
| 11 | 234494393383614 |
| 12 | 15187062546935643 |
| 13 | 1086079262127563445 |
| 14 | 85049134680670591560 |
| 15 | 7241328591814507465712 |
| 16 | 666283956766298002183275 |
[1,3,18,180,2670,54096,1411228,45421776, 1747674405,78485504845,4037946005808, 234494393383614,15187062546935643, 1086079262127563445,85049134680670591560, 7241328591814507465712,666283956766298002183275] |