Add all the A tasks

Task/Arithmetic-Rational/Fortran/arithmetic-rational-2.f

@@ -0,0 +1,28 @@
+program perfect_numbers
+
+  use module_rational
+  implicit none
+  integer, parameter :: n_min = 2
+  integer, parameter :: n_max = 2 ** 19 - 1
+  integer :: n
+  integer :: factor
+  type (rational) :: sum
+
+  do n = n_min, n_max
+    sum = 1 // n
+    factor = 2
+    do
+      if (factor * factor >= n) then
+        exit
+      end if
+      if (modulo (n, factor) == 0) then
+        sum = rational_simplify (sum + (1 // factor) + (factor // n))
+      end if
+      factor = factor + 1
+    end do
+    if (sum % numerator == 1 .and. sum % denominator == 1) then
+      write (*, '(i0)') n
+    end if
+  end do
+
+end program perfect_numbers