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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 7 |
| 5 | 15 |
| 6 | 33 |
| 7 | 77 |
| 8 | 187 |
| 9 | 459 |
| 10 | 1121 |
| 11 | 2717 |
| 12 | 6555 |
| 13 | 15795 |
| 14 | 38081 |
| 15 | 91893 |
| 16 | 221867 |
| 17 | 535755 |
| 18 | 1293633 |
| 19 | 3123277 |
| 20 | 7540187 |
| 21 | 18203139 |
| 22 | 43945441 |
| 23 | 106092997 |
| 24 | 256131435 |
| 25 | 618357915 |
| 26 | 1492851361 |
| 27 | 3604064733 |
| 28 | 8700980827 |
| 29 | 21006018195 |
| 30 | 50713000833 |
[0,0,1,3,7,15,33,77,187,459,1121,2717,6555,15795, 38081,91893,221867,535755,1293633,3123277,7540187, 18203139,43945441,106092997,256131435,618357915, 1492851361,3604064733,8700980827,21006018195, 50713000833] |