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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 12 |
| 5 | 35 |
| 6 | 123 |
| 7 | 421 |
| 8 | 1576 |
| 9 | 5891 |
| 10 | 23087 |
| 11 | 91259 |
| 12 | 370459 |
| 13 | 1519776 |
| 14 | 6337233 |
| 15 | 26681825 |
| 16 | 113581304 |
| 17 | 487443036 |
| 18 | 2108776238 |
| 19 | 9183762845 |
| 20 | 40244481167 |
| 21 | 177314468256 |
| 22 | 785126740297 |
| 23 | 3491955994631 |
| 24 | 15594314705119 |
| 25 | 69899003379185 |
| 26 | 314376552573569 |
| 27 | 1418342696862853 |
| 28 | 6417386874955452 |
[1,1,2,4,12,35,123,421,1576,5891,23087,91259, 370459,1519776,6337233,26681825,113581304, 487443036,2108776238,9183762845,40244481167, 177314468256,785126740297,3491955994631, 15594314705119,69899003379185,314376552573569, 1418342696862853,6417386874955452] |