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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 3 |
| 3 | 18 |
| 4 | 157 |
| 5 | 1776 |
| 6 | 24687 |
| 7 | 407464 |
| 8 | 7792857 |
| 9 | 169594560 |
| 10 | 4141165051 |
| 11 | 112178655744 |
| 12 | 3339749183157 |
| 13 | 108422228887168 |
| 14 | 3812520677598375 |
| 15 | 144372964560581376 |
| 16 | 5858088633723823153 |
| 17 | 253575577033176047616 |
| 18 | 11664031615012086920307 |
| 19 | 568166632439929892761600 |
[1,1,3,18,157,1776,24687,407464,7792857,169594560, 4141165051,112178655744,3339749183157, 108422228887168,3812520677598375, 144372964560581376,5858088633723823153, 253575577033176047616,11664031615012086920307, 568166632439929892761600] |