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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 68 |
| 7 | 1500 |
| 8 | 18468 |
| 9 | 199358 |
| 10 | 2097950 |
| 11 | 21391538 |
| 12 | 214036364 |
| 13 | 2120258590 |
| 14 | 20866289330 |
| 15 | 204450476448 |
| 16 | 1997678664888 |
| 17 | 19484168217576 |
| 18 | 189811510106906 |
| 19 | 1847674840583418 |
| 20 | 17976598424797564 |
| 21 | 174841312778396252 |
[0,0,0,0,0,68,1500,18468,199358,2097950,21391538, 214036364,2120258590,20866289330,204450476448, 1997678664888,19484168217576,189811510106906, 1847674840583418,17976598424797564, 174841312778396252] |