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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 10 |
| 4 | 70 |
| 5 | 672 |
| 6 | 8052 |
| 7 | 116688 |
| 8 | 1980550 |
| 9 | 38584832 |
| 10 | 848550716 |
| 11 | 20798016512 |
| 12 | 562207553180 |
| 13 | 16617377382400 |
| 14 | 533178982025640 |
| 15 | 18456632057456640 |
| 16 | 685638687223902150 |
| 17 | 27207948318401495040 |
| 18 | 1148663601834061166700 |
| 19 | 51407715898046990254080 |
| 20 | 2431161079689601662760500 |
[1,1,2,10,70,672,8052,116688,1980550,38584832, 848550716,20798016512,562207553180,16617377382400, 533178982025640,18456632057456640, 685638687223902150,27207948318401495040, 1148663601834061166700,51407715898046990254080, 2431161079689601662760500] |