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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 28 |
| 3 | 232 |
| 4 | 2092 |
| 5 | 19864 |
| 6 | 195352 |
| 7 | 1970896 |
| 8 | 20275692 |
| 9 | 211825564 |
| 10 | 2240852928 |
| 11 | 23952708696 |
| 12 | 258285519688 |
| 13 | 2806105225928 |
| 14 | 30685515254240 |
| 15 | 337472968923532 |
| 16 | 3730218568024236 |
| 17 | 41417273400310152 |
| 18 | 461722437389957236 |
| 19 | 5166105817092273412 |
[1,4,28,232,2092,19864,195352,1970896,20275692, 211825564,2240852928,23952708696,258285519688, 2806105225928,30685515254240,337472968923532, 3730218568024236,41417273400310152, 461722437389957236,5166105817092273412] |