The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 16 |
| 5 | 50 |
| 6 | 368 |
| 7 | 1764 |
| 8 | 16896 |
| 9 | 109584 |
| 10 | 1297152 |
| 11 | 10628640 |
| 12 | 149944320 |
| 13 | 1486442880 |
| 14 | 24349317120 |
| 15 | 283465647360 |
| 16 | 5287713177600 |
| 17 | 70734282393600 |
| 18 | 1480103564083200 |
| 19 | 22376988058521600 |
| 20 | 519000166327910400 |
| 21 | 8752948036761600000 |
| 22 | 222845873874075648000 |
| 23 | 4148476779335454720000 |
[0,0,2,3,16,50,368,1764,16896,109584,1297152, 10628640,149944320,1486442880,24349317120, 283465647360,5287713177600,70734282393600, 1480103564083200,22376988058521600, 519000166327910400,8752948036761600000, 222845873874075648000,4148476779335454720000] |