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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 81 |
| 5 | 333 |
| 6 | 1424 |
| 7 | 6263 |
| 8 | 28112 |
| 9 | 128166 |
| 10 | 591441 |
| 11 | 2755709 |
| 12 | 12939977 |
| 13 | 61151408 |
| 14 | 290525984 |
| 15 | 1386448835 |
| 16 | 6641603064 |
| 17 | 31919705258 |
| 18 | 153840916734 |
| 19 | 743285720192 |
| 20 | 3598993906365 |
| 21 | 17459804040867 |
| 22 | 84847494634167 |
| 23 | 412954570844012 |
| 24 | 2012623471353633 |
| 25 | 9821151931518819 |
| 26 | 47979118940746443 |
| 27 | 234632815917788513 |
[1,2,6,21,81,333,1424,6263,28112,128166,591441, 2755709,12939977,61151408,290525984,1386448835, 6641603064,31919705258,153840916734,743285720192, 3598993906365,17459804040867,84847494634167, 412954570844012,2012623471353633,9821151931518819, 47979118940746443,234632815917788513] |