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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 6 |
| 4 | 20 |
| 5 | 52 |
| 6 | 180 |
| 7 | 531 |
| 8 | 1935 |
| 9 | 6087 |
| 10 | 23075 |
| 11 | 76002 |
| 12 | 294690 |
| 13 | 1007573 |
| 14 | 3967709 |
| 15 | 13952603 |
| 16 | 55705977 |
| 17 | 200096396 |
| 18 | 808097516 |
| 19 | 2954315100 |
| 20 | 12036963816 |
| 21 | 44673868259 |
| 22 | 183352067367 |
| 23 | 689141233096 |
| 24 | 2846666932970 |
| 25 | 10814730959009 |
| 26 | 44922309300087 |
| 27 | 172272809441244 |
| 28 | 719005305749812 |
| 29 | 2780261740311903 |
[1,1,3,6,20,52,180,531,1935,6087,23075,76002, 294690,1007573,3967709,13952603,55705977, 200096396,808097516,2954315100,12036963816, 44673868259,183352067367,689141233096, 2846666932970,10814730959009,44922309300087, 172272809441244,719005305749812,2780261740311903] |