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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 21 |
| 4 | 126 |
| 5 | 1001 |
| 6 | 10129 |
| 7 | 126006 |
| 8 | 1877593 |
| 9 | 32888637 |
| 10 | 666757418 |
| 11 | 15442626557 |
| 12 | 404271491249 |
| 13 | 11855277004330 |
| 14 | 386411610169757 |
| 15 | 13904155500245141 |
| 16 | 549062380938559062 |
| 17 | 23670411643929747681 |
| 18 | 1108835228310948875297 |
| 19 | 56206315123997801696158 |
| 20 | 3071280303942573508668753 |
| 21 | 180294553591510412499169117 |
[1,2,5,21,126,1001,10129,126006,1877593,32888637, 666757418,15442626557,404271491249,11855277004330, 386411610169757,13904155500245141, 549062380938559062,23670411643929747681, 1108835228310948875297,56206315123997801696158, 3071280303942573508668753, 180294553591510412499169117] |