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| n | a(n) |
|---|---|
| 1 | 18 |
| 2 | 324 |
| 3 | 1326 |
| 4 | 5241 |
| 5 | 17763 |
| 6 | 65094 |
| 7 | 246087 |
| 8 | 887406 |
| 9 | 3238750 |
| 10 | 11948552 |
| 11 | 43643883 |
| 12 | 159571382 |
| 13 | 585152040 |
| 14 | 2141835490 |
| 15 | 7838632143 |
| 16 | 28707385058 |
| 17 | 105103321375 |
| 18 | 384772465146 |
| 19 | 1408810317447 |
| 20 | 5157976273501 |
| 21 | 18884160177390 |
| 22 | 69139905612647 |
[18,324,1326,5241,17763,65094,246087,887406, 3238750,11948552,43643883,159571382,585152040, 2141835490,7838632143,28707385058,105103321375, 384772465146,1408810317447,5157976273501, 18884160177390,69139905612647] |