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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 4 |
| 2 | 22 |
| 3 | 152 |
| 4 | 1251 |
| 5 | 11869 |
| 6 | 126987 |
| 7 | 1508209 |
| 8 | 19651299 |
| 9 | 278321523 |
| 10 | 4253151796 |
| 11 | 69700149063 |
| 12 | 1218679465845 |
| 13 | 22634882689433 |
| 14 | 444893598200458 |
| 15 | 9223269744306877 |
| 16 | 201091581942120957 |
| 17 | 4598872183673896769 |
[1,4,22,152,1251,11869,126987,1508209,19651299, 278321523,4253151796,69700149063,1218679465845, 22634882689433,444893598200458,9223269744306877, 201091581942120957,4598872183673896769] |