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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 75 |
| 6 | 284 |
| 7 | 1109 |
| 8 | 4470 |
| 9 | 18453 |
| 10 | 77433 |
| 11 | 329126 |
| 12 | 1415834 |
| 13 | 6149299 |
| 14 | 26931302 |
| 15 | 118780241 |
| 16 | 527010199 |
| 17 | 2350740211 |
| 18 | 10534962936 |
| 19 | 47408681317 |
| 20 | 214136796301 |
| 21 | 970426128408 |
| 22 | 4410950701961 |
| 23 | 20104046171859 |
| 24 | 91856203336505 |
| 25 | 420644431533937 |
| 26 | 1930293373533896 |
| 27 | 8874862002582146 |
| 28 | 40875930281689623 |
[1,1,2,6,21,75,284,1109,4470,18453,77433,329126, 1415834,6149299,26931302,118780241,527010199, 2350740211,10534962936,47408681317,214136796301, 970426128408,4410950701961,20104046171859, 91856203336505,420644431533937,1930293373533896, 8874862002582146,40875930281689623] |