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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 1 |
| 3 | 7 |
| 4 | 57 |
| 5 | 675 |
| 6 | 9255 |
| 7 | 163095 |
| 8 | 3190965 |
| 9 | 75051075 |
| 10 | 2212976535 |
| 11 | 69624142665 |
| 12 | 2606749381005 |
| 13 | 107980344307605 |
| 14 | 4687299592683015 |
| 15 | 222157161929253705 |
| 16 | 11859617311615438365 |
| 17 | 704152383312290447535 |
| 18 | 43210523173814533171635 |
| 19 | 2910538720151462674819545 |
| 20 | 207666871186142520765307695 |
[0,1,7,57,675,9255,163095,3190965,75051075, 2212976535,69624142665,2606749381005, 107980344307605,4687299592683015, 222157161929253705,11859617311615438365, 704152383312290447535,43210523173814533171635, 2910538720151462674819545, 207666871186142520765307695] |