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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 7 |
| 2 | 20 |
| 3 | 53 |
| 4 | 139 |
| 5 | 364 |
| 6 | 953 |
| 7 | 2495 |
| 8 | 6532 |
| 9 | 17101 |
| 10 | 44771 |
| 11 | 117212 |
| 12 | 306865 |
| 13 | 803383 |
| 14 | 2103284 |
| 15 | 5506469 |
| 16 | 14416123 |
| 17 | 37741900 |
| 18 | 98809577 |
| 19 | 258686831 |
| 20 | 677250916 |
| 21 | 1773065917 |
| 22 | 4641946835 |
| 23 | 12152774588 |
| 24 | 31816376929 |
| 25 | 83296356199 |
| 26 | 218072691668 |
| 27 | 570921718805 |
| 28 | 1494692464747 |
[1,7,20,53,139,364,953,2495,6532,17101,44771, 117212,306865,803383,2103284,5506469,14416123, 37741900,98809577,258686831,677250916,1773065917, 4641946835,12152774588,31816376929,83296356199, 218072691668,570921718805,1494692464747] |