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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 4 |
| 6 | 9 |
| 7 | 20 |
| 8 | 47 |
| 9 | 112 |
| 10 | 273 |
| 11 | 676 |
| 12 | 1694 |
| 13 | 4296 |
| 14 | 10991 |
| 15 | 28350 |
| 16 | 73614 |
| 17 | 192327 |
| 18 | 505093 |
| 19 | 1332801 |
| 20 | 3531598 |
| 21 | 9393501 |
| 22 | 25070735 |
| 23 | 67121670 |
| 24 | 180216260 |
| 25 | 485133376 |
| 26 | 1309101329 |
| 27 | 3540394176 |
| 28 | 9594562328 |
| 29 | 26051397890 |
| 30 | 70861839620 |
[0,0,1,1,2,4,9,20,47,112,273,676,1694,4296,10991, 28350,73614,192327,505093,1332801,3531598,9393501, 25070735,67121670,180216260,485133376,1309101329, 3540394176,9594562328,26051397890,70861839620] |