The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 52 |
| 6 | 457 |
| 7 | 4979 |
| 8 | 64591 |
| 9 | 972906 |
| 10 | 16701834 |
| 11 | 322063458 |
| 12 | 6894918021 |
| 13 | 162316253829 |
| 14 | 4168330738093 |
| 15 | 115980086558470 |
| 16 | 3476156853885992 |
| 17 | 111665862911781864 |
| 18 | 3827642575341002133 |
| 19 | 139457935266705019299 |
| 20 | 5382149182666970080019 |
| 21 | 219344947692643001216702 |
[1,1,2,8,52,457,4979,64591,972906,16701834, 322063458,6894918021,162316253829,4168330738093, 115980086558470,3476156853885992, 111665862911781864,3827642575341002133, 139457935266705019299,5382149182666970080019, 219344947692643001216702] |