A156438 - OEIS

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A156438 as a simple table

n	a(n)
2	2
3	0
4	22
5	7
6	232
7	270
8	9312
9	40416
10	1578064
11	10491480
12	534495232
13	4186295040
14	266388662656
15	2380048630848
16	182963339479264
17	1839487795001024
18	166774503916789696
19	1865501254974930048
20	195842622547532763968

[2,0,22,7,232,270,9312,40416,1578064,10491480, 534495232,4186295040,266388662656,2380048630848, 182963339479264,1839487795001024, 166774503916789696,1865501254974930048, 195842622547532763968]