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A007115 as a simple table
| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 0 |
| 2 | -2 |
| 3 | -9 |
| 4 | -20 |
| 5 | -30 |
| 6 | 66 |
| 7 | 0 |
| 8 | -7216 |
| 9 | -155736 |
| 10 | -2447640 |
| 11 | -40095000 |
| 12 | -696155448 |
| 13 | -13193809200 |
| 14 | -269899395024 |
| 15 | -5951688692040 |
| 16 | -140573490904320 |
| 17 | -3543930826470720 |
| 18 | -94977073790051904 |
| 19 | -2697112556290627200 |
[1,0,-2,-9,-20,-30,66,0,-7216,-155736,-2447640, -40095000,-696155448,-13193809200,-269899395024, -5951688692040,-140573490904320,-3543930826470720, -94977073790051904,-2697112556290627200] |