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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 2 |
| 4 | 8 |
| 5 | 16 |
| 6 | 44 |
| 7 | 104 |
| 8 | 264 |
| 9 | 648 |
| 10 | 1616 |
| 11 | 4000 |
| 12 | 9936 |
| 13 | 24640 |
| 14 | 61152 |
| 15 | 151712 |
| 16 | 376448 |
| 17 | 934016 |
| 18 | 2317504 |
| 19 | 5750144 |
| 20 | 14267264 |
| 21 | 35399808 |
| 22 | 87833856 |
| 23 | 217932800 |
| 24 | 540733696 |
| 25 | 1341665280 |
| 26 | 3328932352 |
| 27 | 8259727872 |
| 28 | 20493989888 |
| 29 | 50849570816 |
| 30 | 126167665664 |
[1,0,2,2,8,16,44,104,264,648,1616,4000,9936,24640, 61152,151712,376448,934016,2317504,5750144, 14267264,35399808,87833856,217932800,540733696, 1341665280,3328932352,8259727872,20493989888, 50849570816,126167665664] |