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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 324 |
| 3 | 858 |
| 4 | 5290 |
| 5 | 27022 |
| 6 | 128292 |
| 7 | 684324 |
| 8 | 3524736 |
| 9 | 17492664 |
| 10 | 91157630 |
| 11 | 466901309 |
| 12 | 2357231531 |
| 13 | 12176328967 |
| 14 | 62219037705 |
| 15 | 316361642076 |
| 16 | 1627284771068 |
| 17 | 8309635888371 |
| 18 | 42388164632017 |
| 19 | 217515758892581 |
| 20 | 1110796489660535 |
[18,324,858,5290,27022,128292,684324,3524736, 17492664,91157630,466901309,2357231531, 12176328967,62219037705,316361642076, 1627284771068,8309635888371,42388164632017, 217515758892581,1110796489660535] |