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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 6 |
| 3 | 20 |
| 4 | 73 |
| 5 | 285 |
| 6 | 1148 |
| 7 | 4779 |
| 8 | 20334 |
| 9 | 88008 |
| 10 | 386678 |
| 11 | 1718210 |
| 12 | 7712724 |
| 13 | 34911184 |
| 14 | 159158001 |
| 15 | 730223827 |
| 16 | 3368483512 |
| 17 | 15614541300 |
| 18 | 72693167654 |
| 19 | 339721530052 |
| 20 | 1593166776075 |
| 21 | 7494694158385 |
| 22 | 35357515510128 |
| 23 | 167237574738609 |
| 24 | 792892967407281 |
| 25 | 3767403585314309 |
| 26 | 17936611598970073 |
| 27 | 85554869014994671 |
[1,2,6,20,73,285,1148,4779,20334,88008,386678, 1718210,7712724,34911184,159158001,730223827, 3368483512,15614541300,72693167654,339721530052, 1593166776075,7494694158385,35357515510128, 167237574738609,792892967407281,3767403585314309, 17936611598970073,85554869014994671] |