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| n | a(n) |
|---|---|
| 0 | 0 |
| 1 | 1 |
| 2 | 0 |
| 3 | 1 |
| 4 | -4 |
| 5 | 25 |
| 6 | -120 |
| 7 | 761 |
| 8 | -5024 |
| 9 | 42065 |
| 10 | -378240 |
| 11 | 3898321 |
| 12 | -42905344 |
| 13 | 521329705 |
| 14 | -6794511360 |
| 15 | 96017526281 |
| 16 | -1448243646464 |
| 17 | 23356125062945 |
| 18 | -399450070548480 |
| 19 | 7240133620964641 |
| 20 | -138422733355024384 |
[0,1,0,1,-4,25,-120,761,-5024,42065,-378240, 3898321,-42905344,521329705,-6794511360, 96017526281,-1448243646464,23356125062945, -399450070548480,7240133620964641, -138422733355024384] |