The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 68 |
| 3 | 1108 |
| 4 | 6812 |
| 5 | 67892 |
| 6 | 509952 |
| 7 | 3890056 |
| 8 | 29428836 |
| 9 | 214600036 |
| 10 | 1561753984 |
| 11 | 11203805186 |
| 12 | 79697223948 |
| 13 | 563151495500 |
| 14 | 3952776211644 |
| 15 | 27603742610922 |
| 16 | 191869394908352 |
| 17 | 1328251534591608 |
| 18 | 9162408587486912 |
| 19 | 63001467075539154 |
[0,68,1108,6812,67892,509952,3890056,29428836, 214600036,1561753984,11203805186,79697223948, 563151495500,3952776211644,27603742610922, 191869394908352,1328251534591608,9162408587486912, 63001467075539154] |