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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 20 |
| 5 | 210 |
| 6 | 792 |
| 7 | 8008 |
| 8 | 31824 |
| 9 | 319770 |
| 10 | 6906900 |
| 11 | 30045015 |
| 12 | 600805296 |
| 13 | 5586853480 |
| 14 | 25518731280 |
| 15 | 239877544005 |
| 16 | 4481381406320 |
| 17 | 79960182801345 |
| 18 | 387221678682300 |
| 19 | 6848956078664700 |
| 20 | 63484158299081520 |
| 21 | 312049055023946856 |
| 22 | 5469191608792974920 |
| 23 | 50825908693881519120 |
[1,2,6,20,210,792,8008,31824,319770,6906900, 30045015,600805296,5586853480,25518731280, 239877544005,4481381406320,79960182801345, 387221678682300,6848956078664700, 63484158299081520,312049055023946856, 5469191608792974920,50825908693881519120] |