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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 30 |
| 4 | 210 |
| 5 | 4830 |
| 6 | 140070 |
| 7 | 5182590 |
| 8 | 222851370 |
| 9 | 10474014390 |
| 10 | 555122762670 |
| 11 | 32752242997530 |
| 12 | 2194400280834510 |
| 13 | 160191220500919230 |
| 14 | 12655106419572619170 |
| 15 | 1050373832824527391110 |
| 16 | 93483271121382937808790 |
| 17 | 9067877298774144967452630 |
| 18 | 2022136637626634327741936490 |
[1,2,6,30,210,4830,140070,5182590,222851370, 10474014390,555122762670,32752242997530, 2194400280834510,160191220500919230, 12655106419572619170,1050373832824527391110, 93483271121382937808790,9067877298774144967452630, 2022136637626634327741936490] |