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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 23 |
| 3 | 937574 |
| 4 | 9717339108198104 |
| 5 | 997945570689257470816576227568765689032610 |
[1,4,23,937574,9717339108198104, 997945570689257470816576227568765689032610] |