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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 11 |
| 5 | 30 |
| 6 | 99 |
| 7 | 321 |
| 8 | 1125 |
| 9 | 3994 |
| 10 | 14669 |
| 11 | 54883 |
| 12 | 210009 |
| 13 | 816899 |
| 14 | 3221481 |
| 15 | 12875307 |
| 16 | 51984975 |
| 17 | 211956185 |
| 18 | 871637092 |
| 19 | 3613651770 |
| 20 | 15086421954 |
| 21 | 63391684221 |
| 22 | 267934026055 |
| 23 | 1138417265769 |
| 24 | 4860596083277 |
| 25 | 20847396593292 |
| 26 | 89793624085992 |
| 27 | 388259714531135 |
| 28 | 1684888139692659 |
| 29 | 7336277575618726 |
[1,1,2,4,11,30,99,321,1125,3994,14669,54883, 210009,816899,3221481,12875307,51984975,211956185, 871637092,3613651770,15086421954,63391684221, 267934026055,1138417265769,4860596083277, 20847396593292,89793624085992,388259714531135, 1684888139692659,7336277575618726] |