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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 74 |
| 4 | 1664 |
| 5 | 99934 |
| 6 | 14096488 |
| 7 | 4803404048 |
| 8 | 3998208473098 |
| 9 | 7963043911683306 |
| 10 | 38560364205334572480 |
| 11 | 449439593711854068531514 |
| 12 | 12671283745052415612872263552 |
| 13 | 862325227959961803770298778601380 |
[2,6,74,1664,99934,14096488,4803404048, 3998208473098,7963043911683306, 38560364205334572480,449439593711854068531514, 12671283745052415612872263552, 862325227959961803770298778601380] |