Data commit

Task/Mertens-function/Arturo/mertens-function.arturo

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+mobius: function [n][
+    if n=0 -> return ""
+    if n=1 -> return 1
+    f: factors.prime n
+
+    if f <> unique f -> return 0
+    if? odd? size f -> return neg 1
+    else -> return 1
+]
+
+mertens: function [z][sum map 1..z => mobius]
+
+print "The first 99 Mertens numbers are:"
+loop split.every:20 [""]++map 1..99 => mertens 'a [
+    print map a 'item -> pad to :string item 2
+]
+
+print ""
+
+mertens1000: map 1..1000 => mertens
+print ["Times M(x) is zero between 1 and 1000:" size select mertens1000 => zero?]
+
+crossed: new 0
+fold mertens1000 [a,b][if and? zero? b not? zero? a -> inc 'crossed, b]
+print ["Times M(x) crosses zero between 1 and 1000:" crossed]