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| n | a(n) |
|---|---|
| 1 | 20 |
| 2 | 68 |
| 3 | 148 |
| 4 | 380 |
| 5 | 740 |
| 6 | 1724 |
| 7 | 3220 |
| 8 | 7196 |
| 9 | 13220 |
| 10 | 28988 |
| 11 | 52948 |
| 12 | 115100 |
| 13 | 210020 |
| 14 | 454844 |
| 15 | 830740 |
| 16 | 1796636 |
| 17 | 3286820 |
[20,68,148,380,740,1724,3220,7196,13220,28988, 52948,115100,210020,454844,830740,1796636,3286820] |