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A250221 as a simple table

na(n)
11
22
311
4-1
516
612
7-1
89
9-1
1011
11-1
12-1
13-1
1411
15-1
168
17-1
18-1
19126
20-1
21-1
22-1
23-1
24-1
25-1
2626
2727
28-1
29-1
30-1
31-1
32-1
33-1
34-1
35-1
3629
3731
38-1
39-1
40-1
41-1
42-1
43-1
44-1
45-1
46-1
47-1
48-1
49-1
50-1
51-1
5233
53-1
54-1
55-1
56-1
57-1
58-1
5919
60-1
61-1
6245
63-1
64-1
65-1
66-1
67-1
68-1
6935
70-1
71-1
728

[1,2,11,-1,16,12,-1,9,-1,11,-1,-1,-1,11,-1,8,-1,
 -1,126,-1,-1,-1,-1,-1,-1,26,27,-1,-1,-1,-1,-1,-1,
 -1,-1,29,31,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
 -1,-1,33,-1,-1,-1,-1,-1,-1,19,-1,-1,45,-1,-1,-1,
 -1,-1,-1,35,-1,-1,8]