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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 18 |
| 4 | 160 |
| 5 | 1120 |
| 6 | 6912 |
| 7 | 39424 |
| 8 | 212992 |
| 9 | 1105920 |
| 10 | 5570560 |
| 11 | 27394048 |
| 12 | 132120576 |
| 13 | 627048448 |
| 14 | 2936012800 |
| 15 | 13589544960 |
| 16 | 62277025792 |
| 17 | 282930970624 |
| 18 | 1275605286912 |
| 19 | 5712306503680 |
| 20 | 25426206392320 |
| 21 | 112562502893568 |
| 22 | 495879744126976 |
| 23 | 2174833999740928 |
| 24 | 9499780463984640 |
[1,18,160,1120,6912,39424,212992,1105920,5570560, 27394048,132120576,627048448,2936012800, 13589544960,62277025792,282930970624, 1275605286912,5712306503680,25426206392320, 112562502893568,495879744126976,2174833999740928, 9499780463984640] |