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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 9 |
| 5 | 24 |
| 6 | 63 |
| 7 | 183 |
| 8 | 537 |
| 9 | 1618 |
| 10 | 5055 |
| 11 | 15861 |
| 12 | 51109 |
| 13 | 166314 |
| 14 | 547505 |
| 15 | 1827009 |
| 16 | 6133802 |
| 17 | 20809959 |
| 18 | 71063163 |
| 19 | 244205379 |
| 20 | 844896468 |
| 21 | 2936454598 |
| 22 | 10260887025 |
| 23 | 36010311788 |
| 24 | 126874109569 |
| 25 | 448803378080 |
| 26 | 1592742931810 |
| 27 | 5671060122989 |
| 28 | 20251948686857 |
| 29 | 72515863744189 |
| 30 | 260339300061495 |
| 31 | 936826545096596 |
[1,1,2,4,9,24,63,183,537,1618,5055,15861,51109, 166314,547505,1827009,6133802,20809959,71063163, 244205379,844896468,2936454598,10260887025, 36010311788,126874109569,448803378080, 1592742931810,5671060122989,20251948686857, 72515863744189,260339300061495,936826545096596] |