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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 6 |
| 3 | 24 |
| 4 | 118 |
| 5 | 686 |
| 6 | 4598 |
| 7 | 34872 |
| 8 | 295044 |
| 9 | 2753958 |
| 10 | 28103804 |
| 11 | 311216626 |
| 12 | 3716341042 |
| 13 | 47597786154 |
| 14 | 650812077852 |
| 15 | 9461423560788 |
| 16 | 145724617925326 |
| 17 | 2370293673319292 |
| 18 | 40600119927220706 |
| 19 | 730458115445479734 |
| 20 | 13772063820971722638 |
[2,6,24,118,686,4598,34872,295044,2753958, 28103804,311216626,3716341042,47597786154, 650812077852,9461423560788,145724617925326, 2370293673319292,40600119927220706, 730458115445479734,13772063820971722638] |