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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 9 |
| 7 | 20 |
| 8 | 50 |
| 9 | 124 |
| 10 | 332 |
| 11 | 895 |
| 12 | 2513 |
| 13 | 7172 |
| 14 | 20994 |
| 15 | 62366 |
| 16 | 188696 |
| 17 | 578717 |
| 18 | 1799999 |
| 19 | 5666257 |
| 20 | 18047319 |
| 21 | 58097540 |
| 22 | 188953756 |
| 23 | 620493315 |
| 24 | 2056582095 |
| 25 | 6877206111 |
| 26 | 23195975865 |
| 27 | 78891742748 |
| 28 | 270505303760 |
| 29 | 934890953041 |
| 30 | 3256230606767 |
[1,1,2,4,9,20,50,124,332,895,2513,7172,20994, 62366,188696,578717,1799999,5666257,18047319, 58097540,188953756,620493315,2056582095, 6877206111,23195975865,78891742748,270505303760, 934890953041,3256230606767] |