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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 1 |
| 3 | 4 |
| 4 | 6 |
| 5 | 15 |
| 6 | 25 |
| 7 | 57 |
| 8 | 103 |
| 9 | 223 |
| 10 | 417 |
| 11 | 898 |
| 12 | 1722 |
| 13 | 3707 |
| 14 | 7211 |
| 15 | 15620 |
| 16 | 30724 |
| 17 | 66939 |
| 18 | 132729 |
| 19 | 290916 |
| 20 | 580680 |
| 21 | 1279281 |
| 22 | 2567397 |
| 23 | 5682009 |
| 24 | 11456481 |
| 25 | 25454265 |
| 26 | 51528969 |
| 27 | 114880470 |
| 28 | 233380592 |
| 29 | 521860455 |
| 30 | 1063460261 |
| 31 | 2384247105 |
[0,1,1,4,6,15,25,57,103,223,417,898,1722,3707, 7211,15620,30724,66939,132729,290916,580680, 1279281,2567397,5682009,11456481,25454265, 51528969,114880470,233380592,521860455,1063460261, 2384247105] |