|
|
本帖最后由 cuikun-186 于 2026-10-13 23:11 编辑
Cui Kun's Identity (for Goldbach partitions)
Definition of symbols
Let N be an even integer, N≥6.
r2(N): the number of ordered prime pairs (p,q) such that p+q=N (Goldbach ordered prime pairs).
π(x): prime-counting function, the number of primes not exceeding x.
C(N): the number of ordered odd composite pairs (c1,c2) satisfying c1+c2=N.
Cui Kun's Identity
r2(N)=C(N)+2π(N-3)-N/2
Derivation idea
For even N≥6, all ordered odd number pairs (a,b) with a+b=N can be classified into four disjoint categories:
1. prime + prime
2. prime + composite
3. composite + prime
4. composite + composite
Counting all four categories and rearranging terms yields the above elementary counting identity.
Important remark
This identity is an elementary combinatorial counting formula over odd integer pairs summing to N. |
|