Data commit

Task/Mertens-function/Ruby/mertens-function.rb

@@ -0,0 +1,18 @@
+require 'prime'
+
+def μ(n)
+  return 1 if self == 1
+  pd = n.prime_division
+  return 0 unless pd.map(&:last).all?(1)
+  pd.size.even? ? 1 : -1
+end
+
+def M(n)
+  (1..n).sum{|n| μ(n)}
+end
+
+(["  "] + (1..199).map{|n|"%2s" % M(n)}).each_slice(20){|line| puts line.join(" ") }
+
+ar = (1..1000).map{|n| M(n)}
+puts "\nThe Mertens function is zero #{ar.count(0)} times in the range (1..1000);"
+puts "it crosses zero #{ar.each_cons(2).count{|m1, m2| m1 != 0 && m2 == 0}} times."