A127111 - OEIS

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A127111 as a simple table

n	a(n)
0	0
1	1
2	4
3	21
4	112
5	705
6	4992
7	40215
8	362496
9	3627855
10	39912960
11	478991205
12	6226974720
13	87178156065
14	1307673722880
15	20922787860975
16	355687417774080
17	6402373671268575
18	121645100223037440
19	2432902007521910925

[0,1,4,21,112,705,4992,40215,362496,3627855, 39912960,478991205,6226974720,87178156065, 1307673722880,20922787860975,355687417774080, 6402373671268575,121645100223037440, 2432902007521910925]