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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 6 |
| 4 | 57 |
| 5 | 750 |
| 6 | 12645 |
| 7 | 260190 |
| 8 | 6322365 |
| 9 | 177181830 |
| 10 | 5625873225 |
| 11 | 199608636150 |
| 12 | 7826601269025 |
| 13 | 336070622037150 |
| 14 | 15684327120386925 |
| 15 | 790493799998652750 |
| 16 | 42790196611446409125 |
| 17 | 2475921578709979149750 |
| 18 | 152499324058939789556625 |
| 19 | 9961887269457311273835750 |
| 20 | 687922376268803482237055625 |
[1,1,6,57,750,12645,260190,6322365,177181830, 5625873225,199608636150,7826601269025, 336070622037150,15684327120386925, 790493799998652750,42790196611446409125, 2475921578709979149750,152499324058939789556625, 9961887269457311273835750, 687922376268803482237055625] |