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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 9 |
| 4 | 27 |
| 5 | 60 |
| 6 | 170 |
| 7 | 377 |
| 8 | 996 |
| 9 | 2288 |
| 10 | 5715 |
| 11 | 13002 |
| 12 | 32321 |
| 13 | 72864 |
| 14 | 175137 |
| 15 | 400039 |
| 16 | 943454 |
| 17 | 2133159 |
| 18 | 4993737 |
| 19 | 11236889 |
| 20 | 25995341 |
| 21 | 58480330 |
| 22 | 133650880 |
| 23 | 299347432 |
| 24 | 681346296 |
| 25 | 1519116099 |
| 26 | 3427954877 |
| 27 | 7631479391 |
| 28 | 17122129103 |
| 29 | 37958987956 |
| 30 | 84819325972 |
| 31 | 187405201004 |
[1,1,4,9,27,60,170,377,996,2288,5715,13002,32321, 72864,175137,400039,943454,2133159,4993737, 11236889,25995341,58480330,133650880,299347432, 681346296,1519116099,3427954877,7631479391, 17122129103,37958987956,84819325972,187405201004] |