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A001991 as a simple table

na(n)
12
22
32
42
52
62
72
82
946
1046
1146
1246
1346
1446
15406
16718
17950
18950
19950
201698
211698
221698
231698
241698
253990
263990
273990
2853510
2977970
3089478
3189478
3289478
3389478
3489478
3589478

[2,2,2,2,2,2,2,2,46,46,46,46,46,46,406,718,950,
 950,950,1698,1698,1698,1698,1698,3990,3990,3990,
 53510,77970,89478,89478,89478,89478,89478,89478]