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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 15 |
| 5 | 54 |
| 6 | 216 |
| 7 | 810 |
| 8 | 3105 |
| 9 | 11745 |
| 10 | 44631 |
| 11 | 169128 |
| 12 | 641520 |
| 13 | 2431944 |
| 14 | 9221121 |
| 15 | 34959195 |
| 16 | 132543135 |
| 17 | 502506990 |
| 18 | 1905156936 |
| 19 | 7222991778 |
| 20 | 27384465825 |
| 21 | 103822372809 |
| 22 | 393620574951 |
| 23 | 1492328843280 |
| 24 | 5657848431840 |
| 25 | 21450531825360 |
[0,0,1,3,15,54,216,810,3105,11745,44631,169128, 641520,2431944,9221121,34959195,132543135, 502506990,1905156936,7222991778,27384465825, 103822372809,393620574951,1492328843280, 5657848431840,21450531825360] |