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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 6 |
| 3 | 45 |
| 4 | 324 |
| 5 | 2349 |
| 6 | 17010 |
| 7 | 123201 |
| 8 | 892296 |
| 9 | 6462585 |
| 10 | 46806174 |
| 11 | 339000309 |
| 12 | 2455257420 |
| 13 | 17782547301 |
| 14 | 128792600586 |
| 15 | 932798529225 |
| 16 | 6755924580624 |
| 17 | 48930734246769 |
| 18 | 354387726706230 |
| 19 | 2566702968458301 |
| 20 | 18589707351105876 |
| 21 | 134638570822759965 |
| 22 | 975138791096512674 |
[0,1,6,45,324,2349,17010,123201,892296,6462585, 46806174,339000309,2455257420,17782547301, 128792600586,932798529225,6755924580624, 48930734246769,354387726706230,2566702968458301, 18589707351105876,134638570822759965, 975138791096512674] |