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| n | a(n) |
|---|---|
| 0 | 2 |
| 1 | 6 |
| 2 | 10 |
| 3 | 28 |
| 4 | 126 |
| 5 | 520 |
| 6 | 1394 |
| 7 | 4440 |
| 8 | 11765 |
| 9 | 35702 |
| 10 | 98202 |
| 11 | 271718 |
| 12 | 736814 |
| 13 | 2012631 |
| 14 | 5478367 |
| 15 | 14867499 |
| 16 | 40448112 |
| 17 | 109944053 |
| 18 | 298170203 |
| 19 | 810416222 |
| 20 | 2200884471 |
| 21 | 5980529528 |
[2,6,10,28,126,520,1394,4440,11765,35702,98202, 271718,736814,2012631,5478367,14867499,40448112, 109944053,298170203,810416222,2200884471, 5980529528] |