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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 4 |
| 2 | 22 |
| 3 | 100 |
| 4 | 466 |
| 5 | 2164 |
| 6 | 10054 |
| 7 | 46708 |
| 8 | 216994 |
| 9 | 1008100 |
| 10 | 4683382 |
| 11 | 21757828 |
| 12 | 101081458 |
| 13 | 469599316 |
| 14 | 2181641638 |
| 15 | 10135364500 |
| 16 | 47086382914 |
| 17 | 218751625156 |
| 18 | 1016265649366 |
| 19 | 4721317472932 |
| 20 | 21934066839826 |
| 21 | 101900219778100 |
[2,4,22,100,466,2164,10054,46708,216994,1008100, 4683382,21757828,101081458,469599316,2181641638, 10135364500,47086382914,218751625156, 1016265649366,4721317472932,21934066839826, 101900219778100] |