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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 3 |
| 4 | 12 |
| 5 | 55 |
| 6 | 210 |
| 7 | 826 |
| 8 | 3136 |
| 9 | 12027 |
| 10 | 45870 |
| 11 | 175846 |
| 12 | 674784 |
| 13 | 2598102 |
| 14 | 10024196 |
| 15 | 38771188 |
| 16 | 150250496 |
| 17 | 583368787 |
| 18 | 2268706134 |
| 19 | 8836184878 |
| 20 | 34461323872 |
| 21 | 134563944322 |
| 22 | 526023515996 |
| 23 | 2058355584748 |
| 24 | 8061896050432 |
| 25 | 31602643220830 |
| 26 | 123979613859660 |
| 27 | 486734822857596 |
[0,0,3,12,55,210,826,3136,12027,45870,175846, 674784,2598102,10024196,38771188,150250496, 583368787,2268706134,8836184878,34461323872, 134563944322,526023515996,2058355584748, 8061896050432,31602643220830,123979613859660, 486734822857596] |