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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 6 |
| 4 | 21 |
| 5 | 75 |
| 6 | 260 |
| 7 | 864 |
| 8 | 2756 |
| 9 | 8485 |
| 10 | 25365 |
| 11 | 74021 |
| 12 | 211814 |
| 13 | 596506 |
| 14 | 1658102 |
| 15 | 4560087 |
| 16 | 12431775 |
| 17 | 33648663 |
| 18 | 90537656 |
| 19 | 242420772 |
| 20 | 646489544 |
| 21 | 1718347081 |
| 22 | 4554820137 |
| 23 | 12046252361 |
| 24 | 31799943626 |
| 25 | 83818097710 |
| 26 | 220650496730 |
| 27 | 580264098939 |
| 28 | 1524688425651 |
| 29 | 4003481631675 |
[1,1,2,6,21,75,260,864,2756,8485,25365,74021, 211814,596506,1658102,4560087,12431775,33648663, 90537656,242420772,646489544,1718347081, 4554820137,12046252361,31799943626,83818097710, 220650496730,580264098939,1524688425651, 4003481631675] |