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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 5 |
| 3 | 18 |
| 4 | 73 |
| 5 | 312 |
| 6 | 1391 |
| 7 | 6406 |
| 8 | 30235 |
| 9 | 145478 |
| 10 | 710951 |
| 11 | 3519248 |
| 12 | 17608681 |
| 13 | 88914250 |
| 14 | 452512229 |
| 15 | 2318774506 |
| 16 | 11953427329 |
| 17 | 61948592936 |
| 18 | 322570037543 |
| 19 | 1686777086942 |
| 20 | 8854240330363 |
| 21 | 46638995523598 |
| 22 | 246443050810895 |
[1,2,5,18,73,312,1391,6406,30235,145478,710951, 3519248,17608681,88914250,452512229,2318774506, 11953427329,61948592936,322570037543, 1686777086942,8854240330363,46638995523598, 246443050810895] |