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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 0 |
| 3 | 1 |
| 4 | 18 |
| 5 | 309 |
| 6 | 6716 |
| 7 | 213308 |
| 8 | 10809896 |
| 9 | 911472580 |
| 10 | 129530643900 |
| 11 | 31095704935575 |
| 12 | 12611311380675900 |
| 13 | 8639383512070631700 |
| 14 | 9995541355360989190800 |
| 15 | 19529076234659969430529200 |
| 16 | 64427185703425668434106855840 |
| 17 | 358869201916137601091798728321296 |
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