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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 31 |
| 2 | 615 |
| 3 | 9995 |
| 4 | 145511 |
| 5 | 1981731 |
| 6 | 25867375 |
| 7 | 328390315 |
| 8 | 4092662871 |
| 9 | 50378487731 |
| 10 | 614988087935 |
| 11 | 7465359578235 |
| 12 | 90280175113831 |
| 13 | 1089001243414531 |
| 14 | 13113567724769295 |
| 15 | 157729903649607755 |
[1,31,615,9995,145511,1981731,25867375,328390315, 4092662871,50378487731,614988087935,7465359578235, 90280175113831,1089001243414531,13113567724769295, 157729903649607755] |