a(n) is the number whose binary representation is A138146(n).

Terms

a(0) =1a(1) =7a(2) =31a(3) =119a(4) =455a(5) =1799a(6) =7175a(7) =28679a(8) =114695a(9) =458759a(10) =1835015a(11) =7340039a(12) =29360135a(13) =117440519a(14) =469762055a(15) =1879048199a(16) =7516192775a(17) =30064771079a(18) =120259084295a(19) =481036337159