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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 7 |
| 4 | 25 |
| 5 | 72 |
| 6 | 278 |
| 7 | 918 |
| 8 | 3678 |
| 9 | 13008 |
| 10 | 53788 |
| 11 | 200502 |
| 12 | 844075 |
| 13 | 3258363 |
| 14 | 13943192 |
| 15 | 55340162 |
| 16 | 239449624 |
| 17 | 970569758 |
| 18 | 4241711654 |
| 19 | 17492540256 |
| 20 | 77030015096 |
| 21 | 322137728727 |
| 22 | 1428245048087 |
| 23 | 6043854822426 |
| 24 | 26944775822220 |
| 25 | 115160638548762 |
| 26 | 515967003565501 |
| 27 | 2224260898468260 |
| 28 | 10007663318362161 |
[1,1,3,7,25,72,278,918,3678,13008,53788,200502, 844075,3258363,13943192,55340162,239449624, 970569758,4241711654,17492540256,77030015096, 322137728727,1428245048087,6043854822426, 26944775822220,115160638548762,515967003565501, 2224260898468260,10007663318362161] |