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A331661 as a simple table

na(n)
11
21
3-3
46
530
6-720
79180
8-79020
9-283500
1041886720
11-1580008680
1244344341000
13-851982076440
14-5914076263200
151972181136416400
16-153108297672649200
178900721288190544400
18-403768420629168268800
199341444542413659205600
20856476985107522346596000

[1,1,-3,6,30,-720,9180,-79020,-283500,41886720,
 -1580008680,44344341000,-851982076440,
 -5914076263200,1972181136416400,
 -153108297672649200,8900721288190544400,
 -403768420629168268800,9341444542413659205600,
 856476985107522346596000]