When we write log, we refer to natural logarithm. Let , , and be positive integers, be a prime and be the th prime. To begin with, we prove that there are at least three type integers that satisfy when holds. We suppose is the number of . According to the following Dusart's inequality
holds for , let be as below.
It is confirmed that holds for . holds for since the first term has a greater divergence velocity than the second term. The following inequalities hold for where and hold.
From the above, it is proved that holds for .
We suppose and hold. Let be an odd integer and the product of all the elements , , …, . We suppose holds.
Let be a positive integer.
Let and be integers. We suppose the following equation and hold.
By the equation (1),
holds. Let be an integer.
When holds, must hold by the equation (2) since is odd. We assume that holds for all where holds after this. Let be a positive integer. We consider the following equation.
By the equation (1),
holds. Let be a positive integer.
Comparing the equations (4) and (5), we find that the second term on the equation (5) is times the one on the equation (4). If holds for all , then it becomes a contradiction since is less than one and if this operation is repeated a finite number of times, then the terms will no longer be integers. Therefore, the assumption is false. When holds, for at least one , the equation (4) does not hold and holds by the congruent expression (3).
When holds for some , one of the elements in must be because holds and they cannot be three times or more multiples of . From the above, it is proved that there are an infinite number of twin prime numbers since at least one of the numbers , , …, must be a prime number when and hold and the sets of numbers between and , excluding and can be taken infinitely by increasing . (Q.E.D.)