a(n) = 17*2^n - 1.

Terms

a(0) =16a(1) =33a(2) =67a(3) =135a(4) =271a(5) =543a(6) =1087a(7) =2175a(8) =4351a(9) =8703a(10) =17407a(11) =34815a(12) =69631a(13) =139263a(14) =278527a(15) =557055a(16) =1114111a(17) =2228223a(18) =4456447a(19) =8912895a(20) =17825791a(21) =35651583a(22) =71303167a(23) =142606335a(24) =285212671a(25) =570425343a(26) =1140850687a(27) =2281701375a(28) =4563402751a(29) =9126805503