a(1)=2, a(n)=2*a(n-1)-floor(sqrt(a(n-1))).

Terms

a(0) =2a(1) =3a(2) =5a(3) =8a(4) =14a(5) =25a(6) =45a(7) =84a(8) =159a(9) =306a(10) =595a(11) =1166a(12) =2298a(13) =4549a(14) =9031a(15) =17967a(16) =35800a(17) =71411a(18) =142555a(19) =284733a(20) =568933a(21) =1137112a(22) =2273158a(23) =4544809a(24) =9087487a(25) =18171960a(26) =36339658a(27) =72673288a(28) =145338052a(29) =290664049