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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 21 |
| 4 | 82 |
| 5 | 321 |
| 6 | 1315 |
| 7 | 5459 |
| 8 | 23101 |
| 9 | 99239 |
| 10 | 430761 |
| 11 | 1885010 |
| 12 | 8314081 |
| 13 | 36891946 |
| 14 | 164646168 |
| 15 | 738475180 |
| 16 | 3325764202 |
| 17 | 15034489911 |
| 18 | 68193338795 |
| 19 | 310244886356 |
| 20 | 1415392174360 |
| 21 | 6473319142842 |
| 22 | 29672579428926 |
| 23 | 136297729801830 |
| 24 | 627265676209046 |
| 25 | 2891910000783213 |
| 26 | 13354629064337700 |
| 27 | 61764320784189527 |
[1,2,6,21,82,321,1315,5459,23101,99239,430761, 1885010,8314081,36891946,164646168,738475180, 3325764202,15034489911,68193338795,310244886356, 1415392174360,6473319142842,29672579428926, 136297729801830,627265676209046,2891910000783213, 13354629064337700,61764320784189527] |