The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 18 |
| 2 | 220 |
| 3 | 2310 |
| 4 | 22561 |
| 5 | 212268 |
| 6 | 1957600 |
| 7 | 17857620 |
| 8 | 161924521 |
| 9 | 1463379918 |
| 10 | 13200803980 |
| 11 | 118959425130 |
| 12 | 1071396569881 |
| 13 | 9646380238968 |
| 14 | 86836484875360 |
| 15 | 781623699024840 |
| 16 | 7035090031526641 |
| 17 | 63318194178965418 |
[1,18,220,2310,22561,212268,1957600,17857620, 161924521,1463379918,13200803980,118959425130, 1071396569881,9646380238968,86836484875360, 781623699024840,7035090031526641, 63318194178965418] |