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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 15 |
| 3 | 153 |
| 4 | 1799 |
| 5 | 22969 |
| 6 | 309479 |
| 7 | 4331175 |
| 8 | 62349575 |
| 9 | 917335467 |
| 10 | 13732751589 |
| 11 | 208509835114 |
| 12 | 3203279694575 |
| 13 | 49701110565986 |
| 14 | 777708690091907 |
| 15 | 12258870836704797 |
| 16 | 194475105262057575 |
| 17 | 3102607480658510165 |
| 18 | 49746656826517452788 |
| 19 | 801205735002960886531 |
| 20 | 12956005807148939155717 |
[1,2,15,153,1799,22969,309479,4331175,62349575, 917335467,13732751589,208509835114,3203279694575, 49701110565986,777708690091907,12258870836704797, 194475105262057575,3102607480658510165, 49746656826517452788,801205735002960886531, 12956005807148939155717] |