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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 7 |
| 6 | 55 |
| 7 | 715 |
| 8 | 4260 |
| 9 | 25603 |
| 10 | 102717 |
| 11 | 408766 |
| 12 | 1258601 |
| 13 | 3851049 |
| 14 | 9814876 |
| 15 | 25170369 |
| 16 | 55987636 |
| 17 | 125991305 |
| 18 | 252719186 |
| 19 | 515720550 |
| 20 | 954717615 |
| 21 | 1803406803 |
| 22 | 3129204953 |
| 23 | 5559159252 |
| 24 | 9151697254 |
| 25 | 15453087022 |
| 26 | 24346596138 |
| 27 | 39398858317 |
[0,0,0,0,7,55,715,4260,25603,102717,408766, 1258601,3851049,9814876,25170369,55987636, 125991305,252719186,515720550,954717615, 1803406803,3129204953,5559159252,9151697254, 15453087022,24346596138,39398858317] |