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| n | a(n) |
|---|---|
| 2 | 1 |
| 3 | 2 |
| 4 | 5 |
| 5 | 12 |
| 6 | 33 |
| 7 | 87 |
| 8 | 252 |
| 9 | 703 |
| 10 | 2105 |
| 11 | 6099 |
| 12 | 18689 |
| 13 | 55639 |
| 14 | 173423 |
| 15 | 526937 |
| 16 | 1664094 |
| 17 | 5137233 |
| 18 | 16393315 |
| 19 | 51255709 |
| 20 | 164951529 |
| 21 | 521138861 |
| 22 | 1688959630 |
| 23 | 5382512216 |
| 24 | 17547919924 |
| 25 | 56335234064 |
| 26 | 184596351277 |
| 27 | 596362337295 |
| 28 | 1962723402375 |
[1,2,5,12,33,87,252,703,2105,6099,18689,55639, 173423,526937,1664094,5137233,16393315,51255709, 164951529,521138861,1688959630,5382512216, 17547919924,56335234064,184596351277,596362337295, 1962723402375] |