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| n | a(n) |
|---|---|
| 1 | 2 |
| 2 | 1 |
| 3 | 2 |
| 4 | 6 |
| 5 | 11 |
| 6 | 27 |
| 7 | 53 |
| 8 | 133 |
| 9 | 310 |
| 10 | 691 |
| 11 | 1722 |
| 12 | 4898 |
| 13 | 13169 |
| 14 | 31188 |
| 15 | 68247 |
| 16 | 151695 |
| 17 | 355719 |
| 18 | 880650 |
| 19 | 2386625 |
| 20 | 7052660 |
| 21 | 20845775 |
| 22 | 57431942 |
| 23 | 145661869 |
| 24 | 346176887 |
| 25 | 792710311 |
| 26 | 1828054653 |
| 27 | 4509979089 |
| 28 | 12381748520 |
| 29 | 37284100779 |
| 30 | 117101693844 |
| 31 | 362950924700 |
[2,1,2,6,11,27,53,133,310,691,1722,4898,13169, 31188,68247,151695,355719,880650,2386625,7052660, 20845775,57431942,145661869,346176887,792710311, 1828054653,4509979089,12381748520,37284100779, 117101693844,362950924700] |