a(n) = 20*2^n + 14.

Terms

a(0) =34a(1) =54a(2) =94a(3) =174a(4) =334a(5) =654a(6) =1294a(7) =2574a(8) =5134a(9) =10254a(10) =20494a(11) =40974a(12) =81934a(13) =163854a(14) =327694a(15) =655374a(16) =1310734a(17) =2621454a(18) =5242894a(19) =10485774a(20) =20971534a(21) =41943054a(22) =83886094a(23) =167772174a(24) =335544334a(25) =671088654a(26) =1342177294a(27) =2684354574a(28) =5368709134a(29) =10737418254