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| n | a(n) |
|---|---|
| 0 | 3 |
| 1 | 18 |
| 2 | 114 |
| 3 | 744 |
| 4 | 4932 |
| 5 | 32952 |
| 6 | 221016 |
| 7 | 1485216 |
| 8 | 9989808 |
| 9 | 67223328 |
| 10 | 452457504 |
| 11 | 3045661824 |
| 12 | 20502553152 |
| 13 | 138020971392 |
| 14 | 929153544576 |
| 15 | 6255074075136 |
| 16 | 42109362770688 |
| 17 | 283481998053888 |
| 18 | 1908413999583744 |
| 19 | 12847536038651904 |
[3,18,114,744,4932,32952,221016,1485216,9989808, 67223328,452457504,3045661824,20502553152, 138020971392,929153544576,6255074075136, 42109362770688,283481998053888,1908413999583744, 12847536038651904] |