The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 4 |
| 3 | 30 |
| 4 | 360 |
| 5 | 5880 |
| 6 | 120960 |
| 7 | 2996280 |
| 8 | 86889600 |
| 9 | 2889976320 |
| 10 | 108501724800 |
| 11 | 4539844108800 |
| 12 | 209497816281600 |
| 13 | 10570762445443200 |
| 14 | 578997352591257600 |
| 15 | 34214810278128480000 |
| 16 | 2169772724008976486400 |
| 17 | 146984464202544531763200 |
[1,1,4,30,360,5880,120960,2996280,86889600, 2889976320,108501724800,4539844108800, 209497816281600,10570762445443200, 578997352591257600,34214810278128480000, 2169772724008976486400,146984464202544531763200] |