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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 1 |
| 2 | 2 |
| 3 | 4 |
| 4 | 10 |
| 5 | 27 |
| 6 | 76 |
| 7 | 222 |
| 8 | 668 |
| 9 | 2048 |
| 10 | 6378 |
| 11 | 20132 |
| 12 | 64234 |
| 13 | 206848 |
| 14 | 671418 |
| 15 | 2194432 |
| 16 | 7215644 |
| 17 | 23853318 |
| 18 | 79229676 |
| 19 | 264288462 |
| 20 | 884987529 |
| 21 | 2973772212 |
| 22 | 10024300890 |
| 23 | 33888946600 |
| 24 | 114872472064 |
| 25 | 390334057172 |
| 26 | 1329347719190 |
| 27 | 4536808055808 |
| 28 | 15513418629884 |
[1,1,2,4,10,27,76,222,668,2048,6378,20132,64234, 206848,671418,2194432,7215644,23853318,79229676, 264288462,884987529,2973772212,10024300890, 33888946600,114872472064,390334057172, 1329347719190,4536808055808,15513418629884] |