initial commit

69.fs

@@ -0,0 +1,26 @@
+module _69
+
+open common
+
+let relativePrimeFunc =
+
+    let primeDivisorArrayByMax max =
+        let isPrime = isPrimeFunByMax (int (System.Math.Ceiling(sqrt (float max))))
+        divisorsInclSelf max |> Array.map (List.filter isPrime)
+
+    let totientArrayByMax max =
+        let pd = primeDivisorArrayByMax max
+        let productFormula n primes =
+            let pFunc prime = 1.0 - 1.0/(float prime)
+            primes 
+            |> List.fold (fun p prime -> p * (pFunc prime)) (float n)
+        pd
+        |> Array.mapi productFormula
+    
+    let indexArray = Array.mapi (fun i e -> (i,e))
+
+    totientArrayByMax 1000000
+    |> indexArray
+    |> Seq.skip 1
+    |> Seq.map (fun (i,t) -> (i, (float i)/t))
+    |> Seq.maxBy snd