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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 1 |
| 4 | 1 |
| 5 | 7 |
| 6 | 15 |
| 7 | 60 |
| 8 | 184 |
| 9 | 747 |
| 10 | 3499 |
| 11 | 25726 |
| 12 | 170389 |
| 13 | 1816278 |
| 14 | 17509129 |
| 15 | 246038108 |
| 16 | 3281197739 |
| 17 | 66149680918 |
| 18 | 1268005261759 |
| 19 | 37496297507935 |
| 20 | 1034674372954972 |
| 21 | 43395951886928470 |
[1,1,1,1,7,15,60,184,747,3499,25726,170389, 1816278,17509129,246038108,3281197739,66149680918, 1268005261759,37496297507935,1034674372954972, 43395951886928470] |