The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 3 |
| 2 | 20 |
| 3 | 165 |
| 4 | 1484 |
| 5 | 13986 |
| 6 | 135960 |
| 7 | 1352637 |
| 8 | 13707980 |
| 9 | 141061206 |
| 10 | 1470489800 |
| 11 | 15500280978 |
| 12 | 164967244792 |
| 13 | 1770548369700 |
| 14 | 19143828730800 |
| 15 | 208347968093085 |
| 16 | 2280730450967820 |
| 17 | 25096531231958670 |
| 18 | 277445318198433000 |
[1,3,20,165,1484,13986,135960,1352637,13707980, 141061206,1470489800,15500280978,164967244792, 1770548369700,19143828730800,208347968093085, 2280730450967820,25096531231958670, 277445318198433000] |