a(0) = 2, a(n) = 2^n + 2 for n>=1.

Terms

a(0) =2a(1) =4a(2) =6a(3) =10a(4) =18a(5) =34a(6) =66a(7) =130a(8) =258a(9) =514a(10) =1026a(11) =2050a(12) =4098a(13) =8194a(14) =16386a(15) =32770a(16) =65538a(17) =131074a(18) =262146a(19) =524290a(20) =1048578a(21) =2097154a(22) =4194306a(23) =8388610a(24) =16777218a(25) =33554434a(26) =67108866a(27) =134217730a(28) =268435458a(29) =536870914