A268884 - OEIS

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A268884 as a simple table

n	a(n)
1	20
2	475
3	9996
4	186732
5	3283890
6	55491832
7	911930096
8	14681855846
9	232688402028
10	3642322709900
11	56444213311842
12	867475989937560
13	13239446101273360
14	200865483664370358
15	3031934392327858732
16	45561723449682618252

[20,475,9996,186732,3283890,55491832,911930096, 14681855846,232688402028,3642322709900, 56444213311842,867475989937560,13239446101273360, 200865483664370358,3031934392327858732, 45561723449682618252]