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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 6 |
| 2 | 88 |
| 3 | 1230 |
| 4 | 17136 |
| 5 | 238678 |
| 6 | 3324360 |
| 7 | 46302366 |
| 8 | 644908768 |
| 9 | 8982420390 |
| 10 | 125108976696 |
| 11 | 1742543253358 |
| 12 | 24270496570320 |
| 13 | 338044408731126 |
| 14 | 4708351225665448 |
| 15 | 65578872750585150 |
| 16 | 913395867282526656 |
| 17 | 12721963269204788038 |
| 18 | 177194089901584505880 |
[0,6,88,1230,17136,238678,3324360,46302366, 644908768,8982420390,125108976696,1742543253358, 24270496570320,338044408731126,4708351225665448, 65578872750585150,913395867282526656, 12721963269204788038,177194089901584505880] |