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A109517 as a simple table
| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 18 |
| 4 | 252 |
| 5 | 4880 |
| 6 | 120750 |
| 7 | 3639384 |
| 8 | 129365880 |
| 9 | 5298720768 |
| 10 | 245738908890 |
| 11 | 12728860100000 |
| 12 | 728372947109940 |
| 13 | 45631105330876416 |
| 14 | 3106354479972026374 |
| 15 | 228329428483544787840 |
| 16 | 18022862954171193750000 |
| 17 | 1520481402538463932186624 |
| 18 | 136531862779634547726146994 |
[1,2,18,252,4880,120750,3639384,129365880, 5298720768,245738908890,12728860100000, 728372947109940,45631105330876416, 3106354479972026374,228329428483544787840, 18022862954171193750000,1520481402538463932186624, 136531862779634547726146994] |