A189048 - OEIS

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A189048 as a simple table

n	a(n)
2	1
3	-1
4	23
5	-1
6	-11
7	-1
8	143
9	-1
10	-2527
11	-1
12	1416533
13	-1
14	-57341
15	-1
16	118522111
17	-1
18	-5749735025
19	-1
20	91546452133
21	-1
22	-1792043646907
23	-1
24	1982765704676693
25	-1

[1,-1,23,-1,-11,-1,143,-1,-2527,-1,1416533,-1, -57341,-1,118522111,-1,-5749735025,-1,91546452133, -1,-1792043646907,-1,1982765704676693,-1]