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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 28 |
| 4 | 120 |
| 5 | 259 |
| 6 | 496 |
| 7 | 8128 |
| 8 | 18990 |
| 9 | 667296 |
| 10 | 1858939 |
| 11 | 2097414 |
| 12 | 2383279 |
| 13 | 4843717 |
| 14 | 33550336 |
| 15 | 150588313 |
| 16 | 186695863 |
| 17 | 188908297 |
[1,6,28,120,259,496,8128,18990,667296,1858939, 2097414,2383279,4843717,33550336,150588313, 186695863,188908297] |