The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 24 |
| 5 | 114 |
| 6 | 674 |
| 7 | 4714 |
| 8 | 37754 |
| 9 | 340404 |
| 10 | 3412176 |
| 11 | 37631268 |
| 12 | 452745470 |
| 13 | 5900431012 |
| 14 | 82802497682 |
| 15 | 1244815252434 |
| 16 | 19958707407096 |
| 17 | 339960096280062 |
| 18 | 6130407887839754 |
| 19 | 116675071758609742 |
| 20 | 2337186717333367706 |
| 21 | 49153251967227002616 |
| 22 | 1082860432463176004544 |
[1,1,2,6,24,114,674,4714,37754,340404,3412176, 37631268,452745470,5900431012,82802497682, 1244815252434,19958707407096,339960096280062, 6130407887839754,116675071758609742, 2337186717333367706,49153251967227002616, 1082860432463176004544] |