a(1) = 1; a(n) is the smallest square > 2*a(n-1).

Terms

a(0) =1a(1) =4a(2) =9a(3) =25a(4) =64a(5) =144a(6) =289a(7) =625a(8) =1296a(9) =2601a(10) =5329a(11) =10816a(12) =21904a(13) =44100a(14) =88209a(15) =177241a(16) =355216a(17) =710649a(18) =1423249a(19) =2849344a(20) =5702544a(21) =11410884a(22) =22829284a(23) =45670564a(24) =91355364a(25) =182736324a(26) =365497924a(27) =730999369a(28) =1462068169a(29) =2924213776