A146259 - OEIS

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A146259 as a simple table

n	a(n)
1	1
2	1
3	1
4	1
5	3
6	13
7	31
8	77
9	447
10	3609
11	25623
12	200309
13	2271887
14	36004709
15	643384137
16	13404301669
17	367224822485
18	12922817223889
19	545705442791831
20	28082761867376669
21	1838300090661189305

[1,1,1,1,3,13,31,77,447,3609,25623,200309,2271887, 36004709,643384137,13404301669,367224822485, 12922817223889,545705442791831,28082761867376669, 1838300090661189305]