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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 49 |
| 6 | 394 |
| 7 | 3893 |
| 8 | 45557 |
| 9 | 615841 |
| 10 | 9441496 |
| 11 | 161851172 |
| 12 | 3067568723 |
| 13 | 63691437874 |
| 14 | 1437654815479 |
| 15 | 35051716688753 |
| 16 | 918001141977977 |
| 17 | 25702588103515456 |
| 18 | 766111524549372556 |
| 19 | 24220624517079803807 |
| 20 | 809529063225201561068 |
| 21 | 28520645910908658449119 |
[1,1,2,8,49,394,3893,45557,615841,9441496, 161851172,3067568723,63691437874,1437654815479, 35051716688753,918001141977977,25702588103515456, 766111524549372556,24220624517079803807, 809529063225201561068,28520645910908658449119] |