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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -3 |
| 2 | 0 |
| 3 | -1 |
| 4 | -3 |
| 5 | -9 |
| 6 | -28 |
| 7 | -90 |
| 8 | -297 |
| 9 | -1001 |
| 10 | -3432 |
| 11 | -11934 |
| 12 | -41990 |
| 13 | -149226 |
| 14 | -534888 |
| 15 | -1931540 |
| 16 | -7020405 |
| 17 | -25662825 |
| 18 | -94287120 |
| 19 | -347993910 |
| 20 | -1289624490 |
| 21 | -4796857230 |
| 22 | -17902146600 |
| 23 | -67016296620 |
| 24 | -251577050010 |
| 25 | -946844533674 |
| 26 | -3572042254128 |
| 27 | -13505406670700 |
[1,-3,0,-1,-3,-9,-28,-90,-297,-1001,-3432,-11934, -41990,-149226,-534888,-1931540,-7020405, -25662825,-94287120,-347993910,-1289624490, -4796857230,-17902146600,-67016296620, -251577050010,-946844533674,-3572042254128, -13505406670700] |