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A147190 as a simple table

na(n)
11
21
31
41
51
61
71
81
91
101
111
121
133
143
157
167
1715
1815
1941
2041
21163
22163
23697
24697
253471
263471
2720005
2820005

[1,1,1,1,1,1,1,1,1,1,1,1,3,3,7,7,15,15,41,41,163,
 163,697,697,3471,3471,20005,20005]