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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 5 |
| 4 | 18 |
| 5 | 66 |
| 6 | 245 |
| 7 | 918 |
| 8 | 3465 |
| 9 | 13156 |
| 10 | 50193 |
| 11 | 192270 |
| 12 | 739024 |
| 13 | 2848860 |
| 14 | 11009778 |
| 15 | 42642460 |
| 16 | 165480975 |
| 17 | 643281480 |
| 18 | 2504501625 |
| 19 | 9764299710 |
| 20 | 38115568260 |
| 21 | 148955040300 |
| 22 | 582714871830 |
| 23 | 2281745337300 |
| 24 | 8942420595810 |
| 25 | 35074414899576 |
| 26 | 137672461877850 |
| 27 | 540756483094828 |
[0,1,1,5,18,66,245,918,3465,13156,50193,192270, 739024,2848860,11009778,42642460,165480975, 643281480,2504501625,9764299710,38115568260, 148955040300,582714871830,2281745337300, 8942420595810,35074414899576,137672461877850, 540756483094828] |