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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 40 |
| 3 | 225 |
| 4 | 961 |
| 5 | 3969 |
| 6 | 16129 |
| 7 | 65025 |
| 8 | 261121 |
| 9 | 1046529 |
| 10 | 4190209 |
| 11 | 16769025 |
| 12 | 67092481 |
| 13 | 268402689 |
| 14 | 1073676289 |
| 15 | 4294836225 |
[1,4,40,225,961,3969,16129,65025,261121,1046529, 4190209,16769025,67092481,268402689,1073676289, 4294836225] |