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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | -1 |
| 2 | 4 |
| 3 | -3 |
| 4 | 20 |
| 5 | 2 |
| 6 | 128 |
| 7 | 173 |
| 8 | 1084 |
| 9 | 2694 |
| 10 | 11408 |
| 11 | 35970 |
| 12 | 136072 |
| 13 | 470756 |
| 14 | 1732928 |
| 15 | 6228989 |
| 16 | 22899692 |
| 17 | 83845406 |
| 18 | 309947888 |
| 19 | 1147367414 |
| 20 | 4269385592 |
| 21 | 15927495836 |
| 22 | 59627571968 |
| 23 | 223804469714 |
| 24 | 842295207896 |
| 25 | 3177355985660 |
| 26 | 12012641100832 |
[1,-1,4,-3,20,2,128,173,1084,2694,11408,35970, 136072,470756,1732928,6228989,22899692,83845406, 309947888,1147367414,4269385592,15927495836, 59627571968,223804469714,842295207896, 3177355985660,12012641100832] |