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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 2 |
| 3 | 7 |
| 4 | 16 |
| 5 | 46 |
| 6 | 114 |
| 7 | 309 |
| 8 | 792 |
| 9 | 2101 |
| 10 | 5456 |
| 11 | 14356 |
| 12 | 37468 |
| 13 | 98281 |
| 14 | 256998 |
| 15 | 673323 |
| 16 | 1761984 |
| 17 | 4614226 |
| 18 | 12078110 |
| 19 | 31624285 |
| 20 | 82787980 |
| 21 | 216750601 |
| 22 | 567446112 |
| 23 | 1485616392 |
| 24 | 3889356696 |
| 25 | 10182528721 |
| 26 | 26658108074 |
| 27 | 69791991919 |
| 28 | 182717549872 |
[0,1,2,7,16,46,114,309,792,2101,5456,14356,37468, 98281,256998,673323,1761984,4614226,12078110, 31624285,82787980,216750601,567446112,1485616392, 3889356696,10182528721,26658108074,69791991919, 182717549872] |