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PROJECT EULER · #0800

Hybrid Integers

Statement only · SolvedOriginal problem ↗

An integer of the form pqqp with prime numbers pq is called a hybrid-integer.
For example, 800=2552 is a hybrid-integer.

We define C(n) to be the number of hybrid-integers less than or equal to n.
You are given C(800)=2 and C(800800)=10790.

Find C(800800800800).

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