a(n) = 2*a(n-1) + 13, a(1)=1.

Terms

a(0) =1a(1) =15a(2) =43a(3) =99a(4) =211a(5) =435a(6) =883a(7) =1779a(8) =3571a(9) =7155a(10) =14323a(11) =28659a(12) =57331a(13) =114675a(14) =229363a(15) =458739a(16) =917491a(17) =1834995a(18) =3670003a(19) =7340019a(20) =14680051a(21) =29360115a(22) =58720243a(23) =117440499a(24) =234881011a(25) =469762035a(26) =939524083a(27) =1879048179a(28) =3758096371