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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 16 |
| 4 | 51 |
| 5 | 180 |
| 6 | 622 |
| 7 | 2288 |
| 8 | 8227 |
| 9 | 30940 |
| 10 | 113882 |
| 11 | 434112 |
| 12 | 1622414 |
| 13 | 6240360 |
| 14 | 23572668 |
| 15 | 91245600 |
| 16 | 347398435 |
| 17 | 1351035180 |
| 18 | 5174839714 |
| 19 | 20197293600 |
| 20 | 77729205658 |
| 21 | 304232711640 |
| 22 | 1175332659332 |
| 23 | 4610721207456 |
| 24 | 17868732968846 |
| 25 | 70228114687640 |
| 26 | 272886854006852 |
[1,2,5,16,51,180,622,2288,8227,30940,113882, 434112,1622414,6240360,23572668,91245600, 347398435,1351035180,5174839714,20197293600, 77729205658,304232711640,1175332659332, 4610721207456,17868732968846,70228114687640, 272886854006852] |