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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 6 |
| 2 | 18 |
| 3 | 52 |
| 4 | 130 |
| 5 | 324 |
| 6 | 756 |
| 7 | 1768 |
| 8 | 3978 |
| 9 | 8980 |
| 10 | 19756 |
| 11 | 43608 |
| 12 | 94484 |
| 13 | 205352 |
| 14 | 440040 |
| 15 | 945616 |
| 16 | 2009434 |
| 17 | 4281012 |
| 18 | 9037692 |
| 19 | 19123960 |
| 20 | 40160316 |
| 21 | 84514936 |
| 22 | 176713048 |
| 23 | 370203312 |
| 24 | 771256900 |
| 25 | 1609622664 |
| 26 | 3343062456 |
| 27 | 6954560368 |
| 28 | 14405875048 |
| 29 | 29885491920 |
| 30 | 61763349968 |
| 31 | 127821667232 |
[1,6,18,52,130,324,756,1768,3978,8980,19756,43608, 94484,205352,440040,945616,2009434,4281012, 9037692,19123960,40160316,84514936,176713048, 370203312,771256900,1609622664,3343062456, 6954560368,14405875048,29885491920,61763349968, 127821667232] |