| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 20 |
| 5 | 170 |
| 6 | 1789 |
| 7 | 22869 |
| 8 | 342222 |
| 9 | 5874840 |
| 10 | 113865786 |
| 11 | 2459446440 |
| 12 | 58588151148 |
| 13 | 1526055579828 |
| 14 | 43149414029604 |
| 15 | 1316279791377810 |
| 16 | 43090904609439900 |
| 17 | 1506889769163738432 |
| 18 | 56062825134853664328 |
| 19 | 2211097753021838716116 |
| 20 | 92149286987928381312972 |
[1,0,1,3,20,170,1789,22869,342222,5874840, 113865786,2459446440,58588151148,1526055579828, 43149414029604,1316279791377810,43090904609439900, 1506889769163738432,56062825134853664328, 2211097753021838716116,92149286987928381312972] |