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| n | a(n) |
|---|---|
| 0 | 3 |
| 1 | 0 |
| 2 | 4 |
| 3 | 5 |
| 4 | 18 |
| 5 | 42 |
| 6 | 115 |
| 7 | 296 |
| 8 | 780 |
| 9 | 2037 |
| 10 | 5338 |
| 11 | 13970 |
| 12 | 36579 |
| 13 | 95760 |
| 14 | 250708 |
| 15 | 656357 |
| 16 | 1718370 |
| 17 | 4498746 |
| 18 | 11777875 |
| 19 | 30834872 |
| 20 | 80726748 |
| 21 | 211345365 |
| 22 | 553309354 |
| 23 | 1448582690 |
| 24 | 3792438723 |
| 25 | 9928733472 |
| 26 | 25993761700 |
| 27 | 68052551621 |
| 28 | 178163893170 |
| 29 | 466439127882 |
| 30 | 1221153490483 |
[3,0,4,5,18,42,115,296,780,2037,5338,13970,36579, 95760,250708,656357,1718370,4498746,11777875, 30834872,80726748,211345365,553309354,1448582690, 3792438723,9928733472,25993761700,68052551621, 178163893170,466439127882,1221153490483] |