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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 1 |
| 3 | 13 |
| 4 | 49 |
| 5 | 481 |
| 6 | 3841 |
| 7 | 38221 |
| 8 | 464353 |
| 9 | 5368609 |
| 10 | 82042561 |
| 11 | 1151767981 |
| 12 | 20242097041 |
| 13 | 342921513793 |
| 14 | 6705416722369 |
| 15 | 133590317946541 |
| 16 | 2880298682358721 |
| 17 | 65597610230669761 |
| 18 | 1556262483879791233 |
| 19 | 39569880403136366029 |
| 20 | 1030778206965403668721 |
[1,1,1,13,49,481,3841,38221,464353,5368609, 82042561,1151767981,20242097041,342921513793, 6705416722369,133590317946541,2880298682358721, 65597610230669761,1556262483879791233, 39569880403136366029,1030778206965403668721] |