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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 5 |
| 3 | 16 |
| 4 | 51 |
| 5 | 180 |
| 6 | 685 |
| 7 | 2735 |
| 8 | 11243 |
| 9 | 47120 |
| 10 | 199945 |
| 11 | 855484 |
| 12 | 3679681 |
| 13 | 15882263 |
| 14 | 68701955 |
| 15 | 297607842 |
| 16 | 1290360591 |
| 17 | 5597964012 |
| 18 | 24294536389 |
| 19 | 105460450143 |
| 20 | 457862871585 |
| 21 | 1988029384006 |
| 22 | 8632497563339 |
| 23 | 37485816423762 |
| 24 | 162782662033991 |
[2,5,16,51,180,685,2735,11243,47120,199945,855484, 3679681,15882263,68701955,297607842,1290360591, 5597964012,24294536389,105460450143,457862871585, 1988029384006,8632497563339,37485816423762, 162782662033991] |