a(n) - 2*a(n-1) = period 2: repeat [3, 0] for n > 0, a(0)=5, a(1)=13.

Terms

a(0) =5a(1) =13a(2) =26a(3) =55a(4) =110a(5) =223a(6) =446a(7) =895a(8) =1790a(9) =3583a(10) =7166a(11) =14335a(12) =28670a(13) =57343a(14) =114686a(15) =229375a(16) =458750a(17) =917503a(18) =1835006a(19) =3670015a(20) =7340030a(21) =14680063a(22) =29360126a(23) =58720255a(24) =117440510a(25) =234881023a(26) =469762046a(27) =939524095a(28) =1879048190a(29) =3758096383