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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 16 |
| 3 | 120 |
| 4 | 946 |
| 5 | 7644 |
| 6 | 62831 |
| 7 | 522784 |
| 8 | 4389779 |
| 9 | 37123554 |
| 10 | 315735122 |
| 11 | 2697813440 |
| 12 | 23140821753 |
| 13 | 199142458570 |
| 14 | 1718554831623 |
| 15 | 14866697304316 |
| 16 | 128879838356309 |
| 17 | 1119350439620210 |
| 18 | 9737942597361615 |
| 19 | 84842252277338304 |
| 20 | 740178198190767003 |
| 21 | 6465231396756806046 |
[1,2,16,120,946,7644,62831,522784,4389779, 37123554,315735122,2697813440,23140821753, 199142458570,1718554831623,14866697304316, 128879838356309,1119350439620210,9737942597361615, 84842252277338304,740178198190767003, 6465231396756806046] |