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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 16 |
| 3 | 69 |
| 4 | 314 |
| 5 | 1588 |
| 6 | 8664 |
| 7 | 48485 |
| 8 | 278067 |
| 9 | 1614600 |
| 10 | 9457286 |
| 11 | 55658849 |
| 12 | 328567895 |
| 13 | 1943405850 |
| 14 | 11507060869 |
| 15 | 68185488380 |
| 16 | 404194144927 |
| 17 | 2396690435419 |
| 18 | 14213377453875 |
| 19 | 84300321175577 |
| 20 | 500017419228606 |
| 21 | 2965913106562548 |
[4,16,69,314,1588,8664,48485,278067,1614600, 9457286,55658849,328567895,1943405850,11507060869, 68185488380,404194144927,2396690435419, 14213377453875,84300321175577,500017419228606, 2965913106562548] |