converging.clj

(defn converging-seq
  [coll]
  (for [[x y] (partition 2 1 (cons ::not-an-element coll)) :while (not (= x y))] y))

(defn converging-seq2
  [[x y & tl]]
  (cond (nil? x) []
	(nil? y) [x]
	(= x y) [x]
	:else (lazy-seq (cons x (converging-seq2 (cons y tl))))))

Fixed problem with sequences starting with nil. (converging-seq [nil 1 2 2]) => [] before.