Data update

Task/Totient-function/Fortran/totient-function.f

@@ -0,0 +1,54 @@
+program totient_function
+    implicit none
+    integer, parameter :: M = 100000
+    integer :: i, j
+    integer, dimension(1:M) :: phi
+    character(len=10) :: is_prime
+    integer :: count100, count1000, count10000, count100000
+
+    ! Initialize phi array
+    do i = 1, M
+        phi(i) = i
+    end do
+
+    ! Compute totient using sieve method
+    do i = 2, M
+        if (phi(i) == i) then  ! i is prime
+            do j = i, M, i
+                phi(j) = (phi(j) / i) * (i - 1)
+            end do
+        end if
+    end do
+
+    ! Display for the first 25 integers
+    print*,'n        phi       prime'
+    print*,repeat('-',30)
+    do i = 1, 25
+        if (phi(i) == i - 1) then
+            is_prime = 'prime'
+        else
+            is_prime = 'not prime'
+        end if
+        print "(i0,t10,i3,t20,a)", i, phi(i), trim(is_prime)
+    end do
+
+    ! Count primes up to specified limits
+    count100 = 0
+    count1000 = 0
+    count10000 = 0
+    count100000 = 0
+    do i = 2, M
+        if (phi(i) == i - 1) then
+            if (i <= 100) count100 = count100 + 1
+            if (i <= 1000) count1000 = count1000 + 1
+            if (i <= 10000) count10000 = count10000 + 1
+            count100000 = count100000 + 1
+        end if
+    end do
+
+    print *, 'Count of primes up to 100:', count100
+    print *, 'Count of primes up to 1,000:', count1000
+    print *, 'Count of primes up to 10,000:', count10000
+    print *, 'Count of primes up to 100,000:', count100000
+
+end program totient_function