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| n | a(n) |
|---|---|
| 0 | 1 |
| 1 | 2 |
| 2 | 0 |
| 3 | -2 |
| 4 | -12 |
| 5 | -42 |
| 6 | -144 |
| 7 | -466 |
| 8 | -1476 |
| 9 | -4522 |
| 10 | -13384 |
| 11 | -37794 |
| 12 | -99964 |
| 13 | -237738 |
| 14 | -455104 |
| 15 | -366706 |
| 16 | 2555276 |
| 17 | 20416150 |
| 18 | 103683976 |
| 19 | 445363518 |
| 20 | 1736519252 |
| 21 | 6310980502 |
| 22 | 21595986320 |
| 23 | 69654711278 |
| 24 | 210206070236 |
| 25 | 581729708502 |
[1,2,0,-2,-12,-42,-144,-466,-1476,-4522,-13384, -37794,-99964,-237738,-455104,-366706,2555276, 20416150,103683976,445363518,1736519252, 6310980502,21595986320,69654711278,210206070236, 581729708502] |