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| n | a(n) |
|---|---|
| 1 | 4 |
| 2 | 13 |
| 3 | 45 |
| 4 | 212 |
| 5 | 1205 |
| 6 | 7754 |
| 7 | 54033 |
| 8 | 397820 |
| 9 | 3049439 |
| 10 | 24107782 |
| 11 | 195301124 |
| 12 | 1613855392 |
| 13 | 13556782136 |
| 14 | 115465571163 |
| 15 | 995112789441 |
| 16 | 8663956923566 |
| 17 | 76105986001922 |
| 18 | 673776966100254 |
| 19 | 6006525932517904 |
| 20 | 53878729432248978 |
[4,13,45,212,1205,7754,54033,397820,3049439, 24107782,195301124,1613855392,13556782136, 115465571163,995112789441,8663956923566, 76105986001922,673776966100254,6006525932517904, 53878729432248978] |