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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 23 |
| 2 | 109 |
| 3 | 407 |
| 4 | 1777 |
| 5 | 7813 |
| 6 | 35245 |
| 7 | 160953 |
| 8 | 742857 |
| 9 | 3455597 |
| 10 | 16177459 |
| 11 | 76129593 |
| 12 | 359815609 |
| 13 | 1706868797 |
| 14 | 8122449787 |
| 15 | 38757778297 |
| 16 | 185382123417 |
| 17 | 888570946797 |
| 18 | 4267072020187 |
| 19 | 20525592779337 |
| 20 | 98881792935527 |
| 21 | 477011872851207 |
[1,23,109,407,1777,7813,35245,160953,742857, 3455597,16177459,76129593,359815609,1706868797, 8122449787,38757778297,185382123417,888570946797, 4267072020187,20525592779337,98881792935527, 477011872851207] |