| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 60 |
| 4 | 28980 |
| 5 | 83445678540 |
| 6 | 439837168811386168898460 |
| 7 | 255732290872293553071304874994266857210112979247740 |
| 8 | 342152277075444487917411768449441971426262505651282338530700909926424044202121143490579209389129867953540 |
[1,2,6,60,28980,83445678540, 439837168811386168898460, 25573229087229355307130487499426685721011297924774\ 0, 34215227707544448791741176844944197142626250565128\ 23385307009099264240442021211434905792093891298679\ 53540] |