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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 2 |
| 2 | 4 |
| 3 | 16 |
| 4 | 28 |
| 5 | 56 |
| 6 | 108 |
| 7 | 216 |
| 8 | 424 |
| 9 | 848 |
| 10 | 1684 |
| 11 | 3368 |
| 12 | 6712 |
| 13 | 13424 |
| 14 | 26808 |
| 15 | 53616 |
| 16 | 107152 |
| 17 | 214304 |
| 18 | 428460 |
| 19 | 856920 |
| 20 | 1713544 |
| 21 | 3427088 |
[2,2,4,16,28,56,108,216,424,848,1684,3368,6712, 13424,26808,53616,107152,214304,428460,856920, 1713544,3427088] |