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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 46 |
| 5 | 116 |
| 6 | 284 |
| 7 | 632 |
| 8 | 1414 |
| 9 | 3102 |
| 10 | 6536 |
| 11 | 13636 |
| 12 | 28020 |
| 13 | 56300 |
| 14 | 111888 |
| 15 | 219608 |
| 16 | 424694 |
| 17 | 813104 |
| 18 | 1540818 |
| 19 | 2888060 |
| 20 | 5366072 |
| 21 | 9884616 |
| 22 | 18050428 |
| 23 | 32713048 |
| 24 | 58851972 |
| 25 | 105113942 |
| 26 | 186505864 |
| 27 | 328821408 |
| 28 | 576153008 |
| 29 | 1003687444 |
| 30 | 1738735728 |
| 31 | 2995837872 |
[1,2,6,20,46,116,284,632,1414,3102,6536,13636, 28020,56300,111888,219608,424694,813104,1540818, 2888060,5366072,9884616,18050428,32713048, 58851972,105113942,186505864,328821408,576153008, 1003687444,1738735728,2995837872] |