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| n | a(n) |
|---|---|
| 1 | 1 |
| 2 | 1 |
| 3 | 2 |
| 4 | 4 |
| 5 | 10 |
| 6 | 41 |
| 7 | 135 |
| 8 | 477 |
| 9 | 1719 |
| 10 | 5987 |
| 11 | 20942 |
| 12 | 72586 |
| 13 | 245893 |
| 14 | 825328 |
| 15 | 2735778 |
| 16 | 8923167 |
| 17 | 28779207 |
| 18 | 91732303 |
| 19 | 288568276 |
| 20 | 898134715 |
| 21 | 2765300373 |
| 22 | 8421195140 |
| 23 | 25394904018 |
| 24 | 75848295457 |
| 25 | 224397367622 |
| 26 | 658053395498 |
| 27 | 1913298309395 |
[1,1,2,4,10,41,135,477,1719,5987,20942,72586, 245893,825328,2735778,8923167,28779207,91732303, 288568276,898134715,2765300373,8421195140, 25394904018,75848295457,224397367622,658053395498, 1913298309395] |