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A061655
as a simple table
n
a(n)
0
2
1
-1
2
-4
3
-40
4
-4960
5
-147166720
6
-299211527038566400
7
-2703337074029927682081937523621232640
[2,-1,-4,-40,-4960,-147166720,-299211527038566400, -2703337074029927682081937523621232640]