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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 4 |
| 3 | 8 |
| 4 | 17 |
| 5 | 42 |
| 6 | 124 |
| 7 | 408 |
| 8 | 1380 |
| 9 | 4616 |
| 10 | 15184 |
| 11 | 49568 |
| 12 | 162518 |
| 13 | 539580 |
| 14 | 1818184 |
| 15 | 6203088 |
| 16 | 21339916 |
| 17 | 73776024 |
| 18 | 255853744 |
| 19 | 889678688 |
| 20 | 3102779785 |
| 21 | 10856555130 |
| 22 | 38115293308 |
| 23 | 134243564056 |
| 24 | 474159194316 |
| 25 | 1678926445272 |
| 26 | 5957812156144 |
| 27 | 21183679310048 |
[1,2,4,8,17,42,124,408,1380,4616,15184,49568, 162518,539580,1818184,6203088,21339916,73776024, 255853744,889678688,3102779785,10856555130, 38115293308,134243564056,474159194316, 1678926445272,5957812156144,21183679310048] |