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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 4 |
| 2 | 8 |
| 3 | 20 |
| 4 | 44 |
| 5 | 88 |
| 6 | 180 |
| 7 | 360 |
| 8 | 724 |
| 9 | 1448 |
| 10 | 2896 |
| 11 | 5792 |
| 12 | 11584 |
| 13 | 23168 |
| 14 | 46340 |
| 15 | 92680 |
| 16 | 185360 |
| 17 | 370724 |
| 18 | 741452 |
| 19 | 1482908 |
| 20 | 2965820 |
| 21 | 5931640 |
| 22 | 11863280 |
| 23 | 23726564 |
| 24 | 47453132 |
| 25 | 94906264 |
| 26 | 189812528 |
| 27 | 379625060 |
| 28 | 759250124 |
| 29 | 1518500248 |
[0,4,8,20,44,88,180,360,724,1448,2896,5792,11584, 23168,46340,92680,185360,370724,741452,1482908, 2965820,5931640,11863280,23726564,47453132, 94906264,189812528,379625060,759250124,1518500248] |