The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 21 |
| 2 | 137 |
| 3 | 1413 |
| 4 | 16110 |
| 5 | 214767 |
| 6 | 3057777 |
| 7 | 42648602 |
| 8 | 564936966 |
| 9 | 7083618786 |
| 10 | 84318189822 |
| 11 | 956390845855 |
| 12 | 10375891940786 |
| 13 | 108038550060777 |
| 14 | 1082857046843897 |
| 15 | 10473029871107227 |
| 16 | 97945268899475975 |
| 17 | 887304577889584770 |
[21,137,1413,16110,214767,3057777,42648602, 564936966,7083618786,84318189822,956390845855, 10375891940786,108038550060777,1082857046843897, 10473029871107227,97945268899475975, 887304577889584770] |