Problem #49
Difficulty: 5%
Prime Permutations
Solution Language: Java
Problem Statement
The arithmetic sequence, 1487, 4817, 8147, in which each of the terms increases by 3330, is unusual in two ways: (i) each of the three terms are prime, and, (ii) each of the 4-digit numbers are permutations of one another.
There are no arithmetic sequences made up of three 1-, 2-, or 3-digit primes, exhibiting this property, but there is one other 4-digit increasing sequence.
What 12-digit number do you form by concatenating the three terms in this sequence?
Approach
The solution involves:
- Generating all 4-digit primes
- Grouping primes that are permutations of each other
- For each group, checking for arithmetic sequences
- Finding sequences where all three terms are prime and form equal differences
- Concatenating the three terms of the non-1487 sequence