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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 14 |
| 5 | 84 |
| 6 | 344 |
| 7 | 2714 |
| 8 | 15850 |
| 9 | 158664 |
| 10 | 1254536 |
| 11 | 15066332 |
| 12 | 151035364 |
| 13 | 2091499222 |
| 14 | 25438986270 |
| 15 | 398610118170 |
| 16 | 5712650790562 |
| 17 | 99963273184972 |
| 18 | 1649446030193764 |
| 19 | 31890910904182000 |
| 20 | 594935710367215600 |
| 21 | 12604160312187654888 |
| 22 | 262094375885982582488 |
[1,1,2,6,14,84,344,2714,15850,158664,1254536, 15066332,151035364,2091499222,25438986270, 398610118170,5712650790562,99963273184972, 1649446030193764,31890910904182000, 594935710367215600,12604160312187654888, 262094375885982582488] |