a(n) = the smallest positive multiple of n with exactly n digits when written in binary.

Terms

a(0) =1a(1) =2a(2) =6a(3) =8a(4) =20a(5) =36a(6) =70a(7) =128a(8) =261a(9) =520a(10) =1034a(11) =2052a(12) =4108a(13) =8204a(14) =16395a(15) =32768a(16) =65552a(17) =131076a(18) =262162a(19) =524300a(20) =1048593a(21) =2097172a(22) =4194326a(23) =8388624a(24) =16777225a(25) =33554456a(26) =67108878a(27) =134217748a(28) =268435484a(29) =536870940