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A128251 as a simple table

na(n)
215
35
4255
539
61295
7150
84095
9410
109999
11915
1220735
131785
1438415
153164
1665535
175220
18104975
198145
20159999
2112155
22234255
2317490
24331775
2524414
26456975
2733215
28614655
2944205
30809999
3157720
321048575
3374120
341336335
3593789
361679615
37117135

[15,5,255,39,1295,150,4095,410,9999,915,20735,
 1785,38415,3164,65535,5220,104975,8145,159999,
 12155,234255,17490,331775,24414,456975,33215,
 614655,44205,809999,57720,1048575,74120,1336335,
 93789,1679615,117135]