MAYBE We are left with following problem, upon which TcT provides the certificate MAYBE. Strict Trs: { terms(N) -> cons(recip(sqr(N)), terms(s(N))) , sqr(s(X)) -> s(add(sqr(X), dbl(X))) , sqr(0()) -> 0() , add(s(X), Y) -> s(add(X, Y)) , add(0(), X) -> X , dbl(s(X)) -> s(s(dbl(X))) , dbl(0()) -> 0() , first(s(X), cons(Y, Z)) -> cons(Y, first(X, Z)) , first(0(), X) -> nil() } Obligation: innermost runtime complexity Answer: MAYBE The input cannot be shown compatible Arrrr..