a(n) = 15*2^n - 1.

Terms

a(0) =14a(1) =29a(2) =59a(3) =119a(4) =239a(5) =479a(6) =959a(7) =1919a(8) =3839a(9) =7679a(10) =15359a(11) =30719a(12) =61439a(13) =122879a(14) =245759a(15) =491519a(16) =983039a(17) =1966079a(18) =3932159a(19) =7864319a(20) =15728639a(21) =31457279a(22) =62914559a(23) =125829119a(24) =251658239a(25) =503316479a(26) =1006632959a(27) =2013265919a(28) =4026531839a(29) =8053063679