a(n) = 10*2^n - 3*A083658(n+2).

Terms

a(0) =1a(1) =5a(2) =13a(3) =35a(4) =79a(5) =185a(6) =397a(7) =875a(8) =1831a(9) =3905a(10) =8053a(11) =16835a(12) =34399a(13) =70985a(14) =144157a(15) =294875a(16) =596311a(17) =1212305a(18) =2444293a(19) =4947635a(20) =9954319a(21) =20085785a(22) =40348717a(23) =81228875a(24) =162989191a(25) =327572705a(26) =656739733a(27) =1318262435a(28) =2641307839a(29) =5296964585