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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 4 |
| 3 | 16 |
| 4 | 77 |
| 5 | 351 |
| 6 | 1747 |
| 7 | 8745 |
| 8 | 44724 |
| 9 | 230765 |
| 10 | 1203567 |
| 11 | 6323074 |
| 12 | 33444084 |
| 13 | 177863517 |
| 14 | 950557538 |
| 15 | 5101540598 |
[1,4,16,77,351,1747,8745,44724,230765,1203567, 6323074,33444084,177863517,950557538,5101540598] |