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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 6 |
| 3 | 9 |
| 4 | 156 |
| 5 | 735 |
| 6 | 9738 |
| 7 | 83181 |
| 8 | 1129656 |
| 9 | 13662459 |
| 10 | 207281190 |
| 11 | 3151269033 |
| 12 | 54457383060 |
| 13 | 980680471095 |
| 14 | 19240001086530 |
| 15 | 397345461622245 |
| 16 | 8763618490102128 |
| 17 | 203472380293912563 |
| 18 | 4991552271140255838 |
| 19 | 128517790560854181537 |
| 20 | 3472936316648987980620 |
[1,0,6,9,156,735,9738,83181,1129656,13662459, 207281190,3151269033,54457383060,980680471095, 19240001086530,397345461622245,8763618490102128, 203472380293912563,4991552271140255838, 128517790560854181537,3472936316648987980620] |