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

Terms

a(0) =1a(1) =5a(2) =11a(3) =21a(4) =39a(5) =73a(6) =139a(7) =269a(8) =527a(9) =1041a(10) =2067a(11) =4117a(12) =8215a(13) =16409a(14) =32795a(15) =65565a(16) =131103a(17) =262177a(18) =524323a(19) =1048613a(20) =2097191a(21) =4194345a(22) =8388651a(23) =16777261a(24) =33554479a(25) =67108913a(26) =134217779a(27) =268435509a(28) =536870967a(29) =1073741881