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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 70 |
| 5 | 248 |
| 6 | 882 |
| 7 | 3140 |
| 8 | 11182 |
| 9 | 39824 |
| 10 | 141834 |
| 11 | 505148 |
| 12 | 1799110 |
| 13 | 6407624 |
| 14 | 22821090 |
| 15 | 81278516 |
| 16 | 289477726 |
| 17 | 1030990208 |
| 18 | 3671926074 |
| 19 | 13077758636 |
| 20 | 46577128054 |
| 21 | 165886901432 |
| 22 | 590814960402 |
| 23 | 2104218684068 |
| 24 | 7494285973006 |
| 25 | 26691295287152 |
| 26 | 95062457807466 |
[1,2,6,20,70,248,882,3140,11182,39824,141834, 505148,1799110,6407624,22821090,81278516, 289477726,1030990208,3671926074,13077758636, 46577128054,165886901432,590814960402, 2104218684068,7494285973006,26691295287152, 95062457807466] |