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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 80 |
| 5 | 294 |
| 6 | 1178 |
| 7 | 4720 |
| 8 | 19796 |
| 9 | 81376 |
| 10 | 346368 |
| 11 | 1465122 |
| 12 | 6331534 |
| 13 | 27192882 |
| 14 | 118745262 |
| 15 | 516568790 |
| 16 | 2274700234 |
| 17 | 9991853262 |
| 18 | 44299962722 |
| 19 | 196064059838 |
| 20 | 874195069474 |
| 21 | 3893785311022 |
| 22 | 17444530696426 |
| 23 | 78101794611148 |
| 24 | 351344326779916 |
| 25 | 1580049080320688 |
| 26 | 7133376499493764 |
| 27 | 32201501988720644 |
[1,2,6,20,80,294,1178,4720,19796,81376,346368, 1465122,6331534,27192882,118745262,516568790, 2274700234,9991853262,44299962722,196064059838, 874195069474,3893785311022,17444530696426, 78101794611148,351344326779916,1580049080320688, 7133376499493764,32201501988720644] |