Time for an 2014 update…

Task/Self-referential-sequence/Groovy/self-referential-sequence-1.groovy

@@ -0,0 +1,13 @@
+Number.metaClass.getSelfReferentialSequence = {
+    def number = delegate as String; def sequence = []
+
+    while (!sequence.contains(number)) {
+        sequence << number
+        def encoded = new StringBuilder()
+        ((number as List).sort().join('').reverse() =~ /(([0-9])\2*)/).each { matcher, text, digit ->
+            encoded.append(text.size()).append(digit)
+        }
+        number = encoded.toString()
+    }
+    sequence
+}

Task/Self-referential-sequence/Groovy/self-referential-sequence-2.groovy

@@ -0,0 +1 @@
+9009.selfReferentialSequence.each { println it }