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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 32 |
| 4 | 196 |
| 5 | 1512 |
| 6 | 13384 |
| 7 | 135872 |
| 8 | 1545744 |
| 9 | 19441952 |
| 10 | 268386784 |
| 11 | 4018603008 |
| 12 | 65021744704 |
| 13 | 1127284876928 |
| 14 | 20880206388864 |
| 15 | 410781080941568 |
| 16 | 8561002328678656 |
| 17 | 188224613741879808 |
| 18 | 4355496092560324096 |
| 19 | 105752112730661347328 |
| 20 | 2688539359466319184896 |
[1,2,6,32,196,1512,13384,135872,1545744,19441952, 268386784,4018603008,65021744704,1127284876928, 20880206388864,410781080941568,8561002328678656, 188224613741879808,4355496092560324096, 105752112730661347328,2688539359466319184896] |