A226731 - OEIS

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A226731 as a simple table

n	a(n)
3	20
4	630
5	36288
6	3326400
7	444787200
8	81729648000
9	19760412672000
10	6082255020441600
11	2322315553259520000
12	1077167364120207360000
13	596585001666576384000000
14	388888194657798291456000000

[20,630,36288,3326400,444787200,81729648000, 19760412672000,6082255020441600, 2322315553259520000,1077167364120207360000, 596585001666576384000000, 388888194657798291456000000]