TRS:
 {               terms(N) -> cons(recip(sqr(N)), terms(s(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, Z)) -> cons(Y, first(X, Z))}
 Fail