Tell me more ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

If we look at the difference between consecutive prime numbers, $p \gt 2$, it always appears to be an even number.

For example, here are the seven consecutive primes starting at the $10^{10th}$ prime.

$p_i = \{252097800623, 252097800629, 252097800637, 252097800667, 252097800737, 252097800743, 252097800839\}$

The differences between the consecutive primes above are $\{6, 8, 30, 70, 6, 96\}$, and are all an even number .

This, of course, is automatic for twin primes since by definition they differ by $2$.

Also, this holds for all balanced primes, A006562 - Balanced primes, since we have $2*p_n = p_{n-1} + p_{n+1}$.

There is a table of such values in A001223 - Differences between consecutive primes on OEIS.

My questions are:

(1) Is it considered a conjecture that the difference between consecutive primes $p \gt 2$ is always an even number?

I wasn't sure if there was some argument regarding Prime Gaps that guarantees such a result and it is easy.

(2) Has this been proven?

Note that I found the Prime Difference Function, but is that the latest?

Regards

share|improve this question
8  
Any two primes greater than $2$ are odd. So their difference is...? – julien Jan 13 at 18:42
@julien: Duh to me! Can a moderator please delete? Thanks! – Amzoti Jan 13 at 18:44
No need to delete...it's a cute question! ;-) – amWhy May 21 at 0:13

1 Answer

up vote 4 down vote accepted

You are thinking way too hard about this.

First, to the question in the title (but not as asked in the text) no: $3-2=1$.

As asked in the text for odd primes, then the difference between two odd numbers is always an even number: $$2p+1 - (2q+1) = 2(p-q).$$

share|improve this answer
2  
In other words, the specific case of consecutive odd primes having an even difference follows from the generality (that two odd numbers have an even difference). – hardmath Jan 13 at 18:46

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.