a(0)=1, a(n) = 3*a(n-1) + 2; a(n) = 2*3^n - 1.

Terms

a(0) =1a(1) =5a(2) =17a(3) =53a(4) =161a(5) =485a(6) =1457a(7) =4373a(8) =13121a(9) =39365a(10) =118097a(11) =354293a(12) =1062881a(13) =3188645a(14) =9565937a(15) =28697813a(16) =86093441a(17) =258280325a(18) =774840977a(19) =2324522933a(20) =6973568801a(21) =20920706405a(22) =62762119217a(23) =188286357653a(24) =564859072961