A215223 - OEIS

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A215223 as a simple table

n	a(n)
1	4
2	12
3	24
4	72
5	120
6	408
7	840
8	2448
9	5760
10	15960
11	39864
12	108024
13	275184
14	728784
15	1895760
16	4998528
17	13033560
18	34250904
19	89602632
20	235157640
21	615871032

[4,12,24,72,120,408,840,2448,5760,15960,39864, 108024,275184,728784,1895760,4998528,13033560, 34250904,89602632,235157640,615871032]