The OEIS is supported by the many generous donors to the OEIS Foundation.
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 6 |
| 4 | 25 |
| 5 | 140 |
| 6 | 1177 |
| 7 | 10738 |
| 8 | 104977 |
| 9 | 1188120 |
| 10 | 15191889 |
| 11 | 211088350 |
| 12 | 3187087209 |
| 13 | 52357837220 |
| 14 | 926871127977 |
| 15 | 17553084005322 |
| 16 | 354581844112801 |
| 17 | 7614153761167920 |
| 18 | 173108509344647457 |
| 19 | 4153655608324341686 |
[1,0,1,6,25,140,1177,10738,104977,1188120, 15191889,211088350,3187087209,52357837220, 926871127977,17553084005322,354581844112801, 7614153761167920,173108509344647457, 4153655608324341686] |