The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 19 |
| 4 | 139 |
| 5 | 979 |
| 6 | 6861 |
| 7 | 48038 |
| 8 | 336278 |
| 9 | 2353958 |
| 10 | 16477720 |
| 11 | 115344057 |
| 12 | 807408417 |
| 13 | 5651858937 |
| 14 | 39563012579 |
| 15 | 276941088076 |
| 16 | 1938587616556 |
| 17 | 13570113315916 |
| 18 | 94990793211438 |
| 19 | 664935552480095 |
| 20 | 4654548867360695 |
[0,2,19,139,979,6861,48038,336278,2353958, 16477720,115344057,807408417,5651858937, 39563012579,276941088076,1938587616556, 13570113315916,94990793211438,664935552480095, 4654548867360695] |