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| n | a(n) |
|---|---|
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 0 |
| 6 | 1 |
| 7 | 9 |
| 8 | 51 |
| 9 | 236 |
| 10 | 979 |
| 11 | 3805 |
| 12 | 14190 |
| 13 | 51488 |
| 14 | 183333 |
| 15 | 644121 |
| 16 | 2241127 |
| 17 | 7741378 |
| 18 | 26593899 |
| 19 | 90971184 |
| 20 | 310159487 |
| 21 | 1054693058 |
| 22 | 3578948942 |
| 23 | 12124108632 |
| 24 | 41015411703 |
| 25 | 138597840864 |
| 26 | 467913141789 |
| 27 | 1578497031981 |
| 28 | 5321685955902 |
| 29 | 17931990439148 |
| 30 | 60397664457791 |
| 31 | 203355625940891 |
[0,0,0,0,1,9,51,236,979,3805,14190,51488,183333, 644121,2241127,7741378,26593899,90971184, 310159487,1054693058,3578948942,12124108632, 41015411703,138597840864,467913141789, 1578497031981,5321685955902,17931990439148, 60397664457791,203355625940891] |