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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 16 |
| 5 | 173 |
| 6 | 1325 |
| 7 | 15936 |
| 8 | 187794 |
| 9 | 2167196 |
| 10 | 25071259 |
| 11 | 290320330 |
| 12 | 3362811279 |
| 13 | 38954814644 |
| 14 | 451260930462 |
| 15 | 5227519694115 |
| 16 | 60556885619049 |
| 17 | 701505602257606 |
| 18 | 8126407466223744 |
| 19 | 94138215587957627 |
| 20 | 1090519135777805628 |
[0,0,1,16,173,1325,15936,187794,2167196,25071259, 290320330,3362811279,38954814644,451260930462, 5227519694115,60556885619049,701505602257606, 8126407466223744,94138215587957627, 1090519135777805628] |