The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 12 |
| 4 | 96 |
| 5 | 720 |
| 6 | 6480 |
| 7 | 60480 |
| 8 | 645120 |
| 9 | 7257600 |
| 10 | 90720000 |
| 11 | 1197504000 |
| 12 | 17244057600 |
| 13 | 261534873600 |
| 14 | 4271736268800 |
| 15 | 73229764608000 |
| 16 | 1339058552832000 |
| 17 | 25609494822912000 |
| 18 | 518592270163968000 |
| 19 | 10948059036794880000 |
| 20 | 243290200817664000000 |
[0,0,2,12,96,720,6480,60480,645120,7257600, 90720000,1197504000,17244057600,261534873600, 4271736268800,73229764608000,1339058552832000, 25609494822912000,518592270163968000, 10948059036794880000,243290200817664000000] |