| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 0 |
| 3 | 0 |
| 4 | 0 |
| 5 | 6 |
| 6 | 150 |
| 7 | 400 |
| 8 | 4080 |
| 9 | 15480 |
| 10 | 127818 |
| 11 | 269340 |
| 12 | 3493680 |
| 13 | 5777190 |
| 14 | 57262450 |
| 15 | 210945182 |
| 16 | 1030388115 |
| 17 | 2493913170 |
| 18 | 32176448060 |
| 19 | 51785999300 |
| 20 | 562228325904 |
| 21 | 1805427491920 |
| 22 | 10438821843750 |
| 23 | 22865672706000 |
[0,0,0,0,6,150,400,4080,15480,127818,269340, 3493680,5777190,57262450,210945182,1030388115, 2493913170,32176448060,51785999300,562228325904, 1805427491920,10438821843750,22865672706000] |