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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 0 |
| 2 | 1 |
| 3 | 3 |
| 4 | 6 |
| 5 | 10 |
| 6 | 15 |
| 7 | 20 |
| 8 | 20 |
| 9 | 0 |
| 10 | -75 |
| 11 | -275 |
| 12 | -725 |
| 13 | -1625 |
| 14 | -3250 |
| 15 | -5875 |
| 16 | -9500 |
| 17 | -13125 |
| 18 | -13125 |
| 19 | 0 |
| 20 | 47500 |
| 21 | 171875 |
| 22 | 450000 |
| 23 | 1006250 |
| 24 | 2012500 |
| 25 | 3640625 |
| 26 | 5890625 |
| 27 | 8140625 |
| 28 | 8140625 |
| 29 | 0 |
| 30 | -29453125 |
| 31 | -106562500 |
| 32 | -278984375 |
| 33 | -623828125 |
| 34 | -1247656250 |
| 35 | -2257031250 |
[0,0,1,3,6,10,15,20,20,0,-75,-275,-725,-1625, -3250,-5875,-9500,-13125,-13125,0,47500,171875, 450000,1006250,2012500,3640625,5890625,8140625, 8140625,0,-29453125,-106562500,-278984375, -623828125,-1247656250,-2257031250] |