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| n | a(n) |
|---|---|
| 0 | -1 |
| 1 | 6 |
| 2 | 38 |
| 3 | 340 |
| 4 | 3482 |
| 5 | 38740 |
| 6 | 457500 |
| 7 | 5654440 |
| 8 | 72412410 |
| 9 | 953696900 |
| 10 | 12844323828 |
| 11 | 176130113432 |
| 12 | 2450987760676 |
| 13 | 34524885571400 |
| 14 | 491309242342264 |
| 15 | 7052495781361488 |
| 16 | 101992452504973882 |
| 17 | 1484590294804096356 |
| 18 | 21732695236734410500 |
| 19 | 319745609409940857144 |
[-1,6,38,340,3482,38740,457500,5654440,72412410, 953696900,12844323828,176130113432,2450987760676, 34524885571400,491309242342264,7052495781361488, 101992452504973882,1484590294804096356, 21732695236734410500,319745609409940857144] |