Solved 92.

README.md

@@ -45,7 +45,6 @@ in many cases the Clojure solution is very different from how I solved
 it in Ruby.  Here is my migration TODO list.  Problems I have solved
 in Ruby, but not yet in Clojure:
 
-* 92
 * 96
 * 97
 * 98

src/dma/euler/p092.clj

@@ -0,0 +1,31 @@
+(ns dma.euler.p092
+  (:use dma.euler.numeric))
+
+;; Cleaner, but slow way to get the next number in the chain
+;;
+;; (defn sum-square-digits [n]
+;;  (sum (map square (digits n))))
+
+(def squares (vec (map square (range 10))))
+
+(defn sum-square-digits [n]
+  (loop [n n sum 0]
+    (if (zero? n)
+      sum
+      (recur (quot n 10) (+ sum (squares (rem n 10)))))))
+
+(let [chain-endings (atom {1 1 89 89})]
+  (defn chain-end [n]
+    (loop [n n chain []]
+      (if-let [end (@chain-endings n)]
+        (do
+          (if (seq chain)
+            (swap! chain-endings #(apply assoc % (interleave chain (repeat end)))))
+          end)
+        (recur (sum-square-digits n) (conj chain n))))))
+
+(defn solution {:answer 8581146} []
+  ;; Note that we pass the number through sum-square-digits first
+  ;; to get it down to a number less than 567 (for 9999999).  That
+  ;; keeps the cache manageable
+  (count (filter #(= 89 (chain-end (sum-square-digits %))) (range 1 10000000))))