Real quadratic fields with class numbers divisible by five
Real quadratic fields with class numbers divisible by five
Conditions are given for a real quadratic field to have class number divisible by five. If 5 does not divide<italic>m</italic>, then a necessary condition for 5 to divide the class number of the real quadratic field with conductor<italic>m</italic>or 5<italic>m</italic>is that 5 divide the class number of a certain cyclic biquadratic …