update_oai-pmh cosmetic improvement on statistics reporting.

scripts/update_oai-pmh.rb

@@ -226,6 +226,8 @@ class SeriesStatistics
     def to_s
         if @series.length == 0
             "N=0"
+        elsif @series.length == 1
+            "N=1 x=#{(mean).signif(2)}"
         else
             "N=#{count} min=#{(min).signif(2)} μ=#{(mean).signif(2)} max=#{(max).signif(2)} σ=#{(standard_deviation).signif(2)}"
         end