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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 5 |
| 4 | 15 |
| 5 | 52 |
| 6 | 203 |
| 7 | 877 |
| 8 | 4140 |
| 9 | 21147 |
| 10 | 115975 |
| 11 | 678570 |
| 12 | 4213596 |
| 13 | 27644383 |
| 14 | 190897649 |
| 15 | 1382919174 |
| 16 | 10479355676 |
| 17 | 82850735298 |
| 18 | 681840170501 |
| 19 | 5828967784989 |
| 20 | 51665915664913 |
| 21 | 473990899143781 |
| 22 | 4493642492511044 |
| 23 | 43959218211619150 |
[1,1,2,5,15,52,203,877,4140,21147,115975,678570, 4213596,27644383,190897649,1382919174,10479355676, 82850735298,681840170501,5828967784989, 51665915664913,473990899143781,4493642492511044, 43959218211619150] |