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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 16 |
| 4 | 45 |
| 5 | 126 |
| 6 | 357 |
| 7 | 1024 |
| 8 | 2979 |
| 9 | 8800 |
| 10 | 26422 |
| 11 | 80688 |
| 12 | 250705 |
| 13 | 792568 |
| 14 | 2548620 |
| 15 | 8331568 |
| 16 | 27667109 |
| 17 | 93241152 |
| 18 | 318569656 |
| 19 | 1102246040 |
| 20 | 3857916552 |
| 21 | 13644697000 |
| 22 | 48716177272 |
| 23 | 175417870080 |
| 24 | 636493447625 |
| 25 | 2325399611652 |
| 26 | 8548381939932 |
| 27 | 31599848465276 |
[1,2,6,16,45,126,357,1024,2979,8800,26422,80688, 250705,792568,2548620,8331568,27667109,93241152, 318569656,1102246040,3857916552,13644697000, 48716177272,175417870080,636493447625, 2325399611652,8548381939932,31599848465276] |