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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 4 |
| 3 | 10 |
| 4 | 36 |
| 5 | 132 |
| 6 | 532 |
| 7 | 2222 |
| 8 | 9584 |
| 9 | 42248 |
| 10 | 189776 |
| 11 | 864830 |
| 12 | 3989656 |
| 13 | 18593424 |
| 14 | 87413444 |
| 15 | 414060796 |
| 16 | 1974260912 |
| 17 | 9467922870 |
| 18 | 45638482068 |
| 19 | 221001289714 |
| 20 | 1074591477112 |
| 21 | 5244497440468 |
| 22 | 25681907242416 |
| 23 | 126149132242490 |
| 24 | 621386729646752 |
| 25 | 3068748094479108 |
[2,4,10,36,132,532,2222,9584,42248,189776,864830, 3989656,18593424,87413444,414060796,1974260912, 9467922870,45638482068,221001289714,1074591477112, 5244497440468,25681907242416,126149132242490, 621386729646752,3068748094479108] |