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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 5 |
| 4 | 18 |
| 5 | 66 |
| 6 | 246 |
| 7 | 924 |
| 8 | 3493 |
| 9 | 13277 |
| 10 | 50697 |
| 11 | 194327 |
| 12 | 747319 |
| 13 | 2882061 |
| 14 | 11142027 |
| 15 | 43167573 |
| 16 | 167561586 |
| 17 | 651513594 |
| 18 | 2537041938 |
| 19 | 9892847952 |
| 20 | 38623197264 |
| 21 | 150959213886 |
| 22 | 590626854072 |
| 23 | 2312979822738 |
| 24 | 9065733950526 |
| 25 | 35561306875380 |
| 26 | 139595183125750 |
[1,0,1,5,18,66,246,924,3493,13277,50697,194327, 747319,2882061,11142027,43167573,167561586, 651513594,2537041938,9892847952,38623197264, 150959213886,590626854072,2312979822738, 9065733950526,35561306875380,139595183125750] |