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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 12 |
| 4 | 35 |
| 5 | 72 |
| 6 | 210 |
| 7 | 440 |
| 8 | 1287 |
| 9 | 2730 |
| 10 | 8008 |
| 11 | 17136 |
| 12 | 50388 |
| 13 | 108528 |
| 14 | 319770 |
| 15 | 692208 |
| 16 | 2042975 |
| 17 | 4440150 |
| 18 | 13123110 |
| 19 | 28614300 |
| 20 | 84672315 |
| 21 | 185122080 |
| 22 | 548354040 |
| 23 | 1201610592 |
| 24 | 3562467300 |
| 25 | 7821594872 |
| 26 | 23206929840 |
| 27 | 51037462560 |
| 28 | 151532656696 |
[1,2,6,12,35,72,210,440,1287,2730,8008,17136, 50388,108528,319770,692208,2042975,4440150, 13123110,28614300,84672315,185122080,548354040, 1201610592,3562467300,7821594872,23206929840, 51037462560,151532656696] |