2^n+1 appears in A109732 at position a(n).

Terms

a(0) =2a(1) =5a(2) =30a(3) =38a(4) =201a(5) =242a(6) =689a(7) =1806a(8) =7175a(9) =10839a(10) =21474a(11) =64607a(12) =290563a(13) =290579a(14) =581260a(15) =872576a(16) =2617577a(17) =5238258a(18) =7858320a(19) =19886365a(20) =47140605a(21) =70713773a(22) =212133736