The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 1 |
| 3 | 1 |
| 4 | 2 |
| 5 | 3 |
| 6 | 6 |
| 7 | 15 |
| 8 | 41 |
| 9 | 120 |
| 10 | 390 |
| 11 | 1356 |
| 12 | 5040 |
| 13 | 19885 |
| 14 | 82835 |
| 15 | 362880 |
| 16 | 1665838 |
| 17 | 7988888 |
| 18 | 39916800 |
| 19 | 207304279 |
| 20 | 1116669004 |
| 21 | 6227020800 |
| 22 | 35886673907 |
| 23 | 213407853923 |
| 24 | 1307674368000 |
| 25 | 8245960182039 |
| 26 | 53446811415730 |
| 27 | 355687428096000 |
| 28 | 2427977164711193 |
| 29 | 16984208960998390 |
[2,1,1,2,3,6,15,41,120,390,1356,5040,19885,82835, 362880,1665838,7988888,39916800,207304279, 1116669004,6227020800,35886673907,213407853923, 1307674368000,8245960182039,53446811415730, 355687428096000,2427977164711193, 16984208960998390] |