diff --git a/sequence.ml b/sequence.ml
index fe48790..99ae6e9 100644
--- a/sequence.ml
+++ b/sequence.ml
@@ -226,6 +226,14 @@ let unfoldr f b =
   in
   from_iter (fun k -> unfold k b)
 
+(** Sequence of intermediate results *)
+let scan f acc seq =
+  from_iter
+    (fun k ->
+      k acc;
+      let acc = ref acc in
+      seq (fun elt -> let acc' = f !acc elt in k acc'; acc := acc'))
+
 (** Max element of the sequence, using the given comparison
     function. A default element has to be provided. *)
 let max ?(lt=fun x y -> x < y) seq m =
diff --git a/sequence.mli b/sequence.mli
index f6ef94b..aab1f0d 100644
--- a/sequence.mli
+++ b/sequence.mli
@@ -119,6 +119,9 @@ val unfoldr : ('b -> ('a * 'b) option) -> 'b -> 'a t
       yields [Some (x,b')] then [x] is returned
       and unfoldr recurses with [b']. *)
 
+val scan : ('b -> 'a -> 'b) -> 'b -> 'a t -> 'b t
+  (** Sequence of intermediate results *)
+
 val max : ?lt:('a -> 'a -> bool) -> 'a t -> 'a -> 'a
   (** Max element of the sequence, using the given comparison
       function. A default element has to be provided. *)