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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 20 |
| 6 | 70 |
| 7 | 255 |
| 8 | 961 |
| 9 | 3717 |
| 10 | 14663 |
| 11 | 58758 |
| 12 | 238524 |
| 13 | 978844 |
| 14 | 4054152 |
| 15 | 16924986 |
| 16 | 71145392 |
| 17 | 300876074 |
| 18 | 1279225578 |
| 19 | 5464762332 |
| 20 | 23444755016 |
| 21 | 100968932096 |
| 22 | 436355661280 |
| 23 | 1891770895672 |
| 24 | 8225329914410 |
| 25 | 35858439130786 |
| 26 | 156708088823482 |
| 27 | 686392551655052 |
[1,1,2,6,20,70,255,961,3717,14663,58758,238524, 978844,4054152,16924986,71145392,300876074, 1279225578,5464762332,23444755016,100968932096, 436355661280,1891770895672,8225329914410, 35858439130786,156708088823482,686392551655052] |