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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 35 |
| 3 | 140 |
| 4 | 490 |
| 5 | 1541 |
| 6 | 4480 |
| 7 | 12195 |
| 8 | 31465 |
| 9 | 77525 |
| 10 | 183626 |
| 11 | 420077 |
| 12 | 932030 |
| 13 | 2011905 |
| 14 | 4237130 |
| 15 | 8725671 |
| 16 | 17605602 |
| 17 | 34861815 |
| 18 | 67848095 |
| 19 | 129946805 |
| 20 | 245203642 |
| 21 | 456303872 |
| 22 | 838178470 |
| 23 | 1520969100 |
| 24 | 2728472695 |
| 25 | 4841909821 |
| 26 | 8504898720 |
| 27 | 14794863270 |
| 28 | 25500965320 |
[1,7,35,140,490,1541,4480,12195,31465,77525, 183626,420077,932030,2011905,4237130,8725671, 17605602,34861815,67848095,129946805,245203642, 456303872,838178470,1520969100,2728472695, 4841909821,8504898720,14794863270,25500965320] |