(VAR N X Y) (RULES 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) half(0) -> 0 half(s(0)) -> 0 half(s(s(X))) -> s(half(X)) half(dbl(X)) -> X )