TRS:
 {            terms(N) -> cons(recip(sqr(N))),
              sqr(0()) -> 0(),
             sqr(s(X)) -> s(add(sqr(X), dbl(X))),
              dbl(0()) -> 0(),
             dbl(s(X)) -> s(s(dbl(X))),
           add(0(), X) -> X,
          add(s(X), Y) -> s(add(X, Y)),
         first(0(), X) -> nil(),
  first(s(X), cons(Y)) -> cons(Y)}
 Fail