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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 21 |
| 2 | 168 |
| 3 | 825 |
| 4 | 3003 |
| 5 | 8918 |
| 6 | 22848 |
| 7 | 52326 |
| 8 | 109725 |
| 9 | 214291 |
| 10 | 394680 |
| 11 | 692055 |
| 12 | 1163799 |
| 13 | 1887900 |
| 14 | 2968064 |
| 15 | 4539612 |
| 16 | 6776217 |
| 17 | 9897537 |
| 18 | 14177800 |
| 19 | 19955397 |
| 20 | 27643539 |
| 21 | 37742034 |
| 22 | 50850240 |
| 23 | 67681250 |
| 24 | 89077365 |
| 25 | 116026911 |
| 26 | 149682456 |
| 27 | 191380483 |
[1,21,168,825,3003,8918,22848,52326,109725,214291, 394680,692055,1163799,1887900,2968064,4539612, 6776217,9897537,14177800,19955397,27643539, 37742034,50850240,67681250,89077365,116026911, 149682456,191380483] |