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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 2 |
| 4 | 8 |
| 5 | 22 |
| 6 | 72 |
| 7 | 218 |
| 8 | 691 |
| 9 | 2158 |
| 10 | 6833 |
| 11 | 21612 |
| 12 | 68726 |
| 13 | 218892 |
| 14 | 699197 |
| 15 | 2237450 |
| 16 | 7174018 |
| 17 | 23038582 |
| 18 | 74097134 |
| 19 | 238625222 |
| 20 | 769407486 |
| 21 | 2483532218 |
| 22 | 8024499657 |
| 23 | 25951580444 |
| 24 | 83999410292 |
| 25 | 272098963300 |
| 26 | 882045339733 |
| 27 | 2861184745710 |
| 28 | 9286923094550 |
| 29 | 30161343633746 |
[0,0,1,2,8,22,72,218,691,2158,6833,21612,68726, 218892,699197,2237450,7174018,23038582,74097134, 238625222,769407486,2483532218,8024499657, 25951580444,83999410292,272098963300,882045339733, 2861184745710,9286923094550,30161343633746] |