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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 18 |
| 2 | 290 |
| 3 | 4914 |
| 4 | 83522 |
| 5 | 1419858 |
| 6 | 24137570 |
| 7 | 410338674 |
| 8 | 6975757442 |
| 9 | 118587876498 |
| 10 | 2015993900450 |
| 11 | 34271896307634 |
| 12 | 582622237229762 |
| 13 | 9904578032905938 |
| 14 | 168377826559400930 |
| 15 | 2862423051509815794 |
| 16 | 48661191875666868482 |
| 17 | 827240261886336764178 |
| 18 | 14063084452067724991010 |
[2,18,290,4914,83522,1419858,24137570,410338674, 6975757442,118587876498,2015993900450, 34271896307634,582622237229762,9904578032905938, 168377826559400930,2862423051509815794, 48661191875666868482,827240261886336764178, 14063084452067724991010] |