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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 6 |
| 3 | 18 |
| 4 | 58 |
| 5 | 140 |
| 6 | 352 |
| 7 | 776 |
| 8 | 1752 |
| 9 | 3696 |
| 10 | 7904 |
| 11 | 16288 |
| 12 | 33824 |
| 13 | 68800 |
| 14 | 140544 |
| 15 | 283776 |
| 16 | 574336 |
| 17 | 1154816 |
| 18 | 2324992 |
| 19 | 4663808 |
| 20 | 9361920 |
| 21 | 18754560 |
| 22 | 37584896 |
| 23 | 75237376 |
| 24 | 150640640 |
| 25 | 301428736 |
| 26 | 603217920 |
| 27 | 1206755328 |
| 28 | 2414288896 |
| 29 | 4829265920 |
[1,6,18,58,140,352,776,1752,3696,7904,16288,33824, 68800,140544,283776,574336,1154816,2324992, 4663808,9361920,18754560,37584896,75237376, 150640640,301428736,603217920,1206755328, 2414288896,4829265920] |