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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 4 |
| 3 | 2 |
| 4 | 28 |
| 5 | 26 |
| 6 | 168 |
| 7 | 214 |
| 8 | 1140 |
| 9 | 1882 |
| 10 | 7930 |
| 11 | 15222 |
| 12 | 56732 |
| 13 | 122760 |
| 14 | 416928 |
| 15 | 975508 |
| 16 | 3116724 |
| 17 | 7715598 |
| 18 | 23651892 |
| 19 | 60875844 |
| 20 | 181428684 |
| 21 | 479853296 |
| 22 | 1403488666 |
| 23 | 3783362306 |
| 24 | 10927395294 |
[0,4,2,28,26,168,214,1140,1882,7930,15222,56732, 122760,416928,975508,3116724,7715598,23651892, 60875844,181428684,479853296,1403488666, 3783362306,10927395294] |