| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 126 |
| 4 | 2032 |
| 5 | 20502 |
| 6 | 160696 |
| 7 | 929880 |
| 8 | 4117520 |
| 9 | 15037036 |
| 10 | 47368960 |
| 11 | 132577826 |
| 12 | 336828368 |
| 13 | 789558314 |
| 14 | 1729320120 |
| 15 | 3574328936 |
| 16 | 7027309888 |
| 17 | 13226773092 |
| 18 | 23959787480 |
| 19 | 41954706558 |
| 20 | 71276149776 |
| 21 | 117848892710 |
| 22 | 190142197976 |
[0,0,126,2032,20502,160696,929880,4117520, 15037036,47368960,132577826,336828368,789558314, 1729320120,3574328936,7027309888,13226773092, 23959787480,41954706558,71276149776,117848892710, 190142197976] |