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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 21 |
| 3 | 174 |
| 4 | 1509 |
| 5 | 13473 |
| 6 | 122580 |
| 7 | 1129999 |
| 8 | 10518477 |
| 9 | 98644395 |
| 10 | 930607321 |
| 11 | 8821717743 |
| 12 | 83960385396 |
| 13 | 801783097911 |
| 14 | 7678690148647 |
| 15 | 73721697254874 |
| 16 | 709323064431597 |
| 17 | 6837868454315828 |
| 18 | 66028546945097793 |
| 19 | 638555320797561440 |
| 20 | 6183787002091288969 |
| 21 | 59957399899953193063 |
[1,3,21,174,1509,13473,122580,1129999,10518477, 98644395,930607321,8821717743,83960385396, 801783097911,7678690148647,73721697254874, 709323064431597,6837868454315828, 66028546945097793,638555320797561440, 6183787002091288969,59957399899953193063] |