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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 4 |
| 3 | 12 |
| 4 | 33 |
| 5 | 88 |
| 6 | 232 |
| 7 | 609 |
| 8 | 1596 |
| 9 | 4180 |
| 10 | 10945 |
| 11 | 28656 |
| 12 | 75024 |
| 13 | 196417 |
| 14 | 514228 |
| 15 | 1346268 |
| 16 | 3524577 |
| 17 | 9227464 |
| 18 | 24157816 |
| 19 | 63245985 |
| 20 | 165580140 |
| 21 | 433494436 |
| 22 | 1134903169 |
| 23 | 2971215072 |
| 24 | 7778742048 |
| 25 | 20365011073 |
| 26 | 53316291172 |
| 27 | 139583862444 |
| 28 | 365435296161 |
| 29 | 956722026040 |
[0,1,4,12,33,88,232,609,1596,4180,10945,28656, 75024,196417,514228,1346268,3524577,9227464, 24157816,63245985,165580140,433494436,1134903169, 2971215072,7778742048,20365011073,53316291172, 139583862444,365435296161,956722026040] |