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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 4 |
| 6 | 17 |
| 7 | 189 |
| 8 | 1586 |
| 9 | 19740 |
| 10 | 226874 |
| 11 | 3292668 |
| 12 | 47746676 |
| 13 | 809546512 |
| 14 | 14151766886 |
| 15 | 277125258626 |
| 16 | 5666164695014 |
| 17 | 126471592770198 |
| 18 | 2959743309058116 |
| 19 | 74377876827534538 |
| 20 | 1960097093923279152 |
[1,1,1,1,4,17,189,1586,19740,226874,3292668, 47746676,809546512,14151766886,277125258626, 5666164695014,126471592770198,2959743309058116, 74377876827534538,1960097093923279152] |