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

Terms

a(0) =1a(1) =5a(2) =12a(3) =23a(4) =40a(5) =67a(6) =112a(7) =191a(8) =336a(9) =611a(10) =1144a(11) =2191a(12) =4264a(13) =8387a(14) =16608a(15) =33023a(16) =65824a(17) =131395a(18) =262504a(19) =524687a(20) =1049016a(21) =2097635a(22) =4194832a(23) =8389183a(24) =16777840a(25) =33555107a(26) =67109592a(27) =134218511a(28) =268436296a(29) =536871811