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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 14 |
| 5 | 35 |
| 6 | 125 |
| 7 | 371 |
| 8 | 1238 |
| 9 | 3909 |
| 10 | 12847 |
| 11 | 41580 |
| 12 | 136577 |
| 13 | 447187 |
| 14 | 1473341 |
| 15 | 4855703 |
| 16 | 16053830 |
| 17 | 53138243 |
| 18 | 176233967 |
| 19 | 585202261 |
| 20 | 1945964079 |
| 21 | 6478043120 |
| 22 | 21588979876 |
| 23 | 72016891508 |
| 24 | 240452892569 |
| 25 | 803489258285 |
| 26 | 2686964354375 |
| 27 | 8991840800136 |
| 28 | 30110638705889 |
[1,0,2,3,14,35,125,371,1238,3909,12847,41580, 136577,447187,1473341,4855703,16053830,53138243, 176233967,585202261,1945964079,6478043120, 21588979876,72016891508,240452892569,803489258285, 2686964354375,8991840800136,30110638705889] |