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| n | a(n) |
|---|---|
| 1 | 0 |
| 2 | 2 |
| 3 | 3 |
| 4 | 4 |
| 5 | 40 |
| 6 | 210 |
| 7 | 1477 |
| 8 | 11672 |
| 9 | 104256 |
| 10 | 1036050 |
| 11 | 11338855 |
| 12 | 135494844 |
| 13 | 1755206648 |
| 14 | 24498813794 |
| 15 | 366526605705 |
| 16 | 5851140525680 |
| 17 | 99271367764480 |
| 18 | 1783734385752162 |
| 19 | 33837677493828171 |
| 20 | 675799125332580020 |
| 21 | 14173726082929399560 |
| 22 | 311462297063636041906 |
[0,2,3,4,40,210,1477,11672,104256,1036050, 11338855,135494844,1755206648,24498813794, 366526605705,5851140525680,99271367764480, 1783734385752162,33837677493828171, 675799125332580020,14173726082929399560, 311462297063636041906] |