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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 2 |
| 3 | 2 |
| 4 | 7 |
| 5 | 13 |
| 6 | 110 |
| 7 | 440 |
| 8 | 7010 |
| 9 | 34814 |
| 10 | 709332 |
| 11 | 4108632 |
| 12 | 100368324 |
| 13 | 667960824 |
| 14 | 18944759304 |
| 15 | 142719383676 |
| 16 | 4596517872930 |
| 17 | 38710991748930 |
| 18 | 1392671800456580 |
| 19 | 12976446818207108 |
| 20 | 514918876680042334 |
| 21 | 5262123025959154234 |
[1,2,2,7,13,110,440,7010,34814,709332,4108632, 100368324,667960824,18944759304,142719383676, 4596517872930,38710991748930,1392671800456580, 12976446818207108,514918876680042334, 5262123025959154234] |