A056195 - OEIS

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A056195 as a simple table

n	a(n)
1	1
2	2
3	6
4	3
5	15
6	720
7	5040
8	5040
9	45360
10	3628800
11	39916800
12	17740800
13	230630400
14	403603200
15	1307674368
16	20922789888
17	355687428096
18	51218989645824
19	973160803270656
20	2432902008176640000
21	5516784599040000

[1,2,6,3,15,720,5040,5040,45360,3628800,39916800, 17740800,230630400,403603200,1307674368, 20922789888,355687428096,51218989645824, 973160803270656,2432902008176640000, 5516784599040000]