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A003261 as a simple table

na(n)
11
27
323
463
5159
6383
7895
82047
94607
1010239
1122527
1249151
13106495
14229375
15491519
161048575
172228223
184718591
199961471
2020971519
2144040191
2292274687
23192937983
24402653183
25838860799
261744830463
273623878655
287516192767

[1,7,23,63,159,383,895,2047,4607,10239,22527,
 49151,106495,229375,491519,1048575,2228223,
 4718591,9961471,20971519,44040191,92274687,
 192937983,402653183,838860799,1744830463,
 3623878655,7516192767]