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A178488
as a simple table
n
a(n)
1
2
2
4
3
9
4
10
5
11
6
12
7
15
8
25
9
31
10
46
11
53
12
78
13
318
14
615
15
955
16
1646
17
2669
18
2672
19
3515
20
7689
[2,4,9,10,11,12,15,25,31,46,53,78,318,615,955, 1646,2669,2672,3515,7689]