Prime digit replacement: https://projecteuler.net/problem=51
Find the smallest prime which, by replacing part of the number (not necessarily adjacent digits) with the same digit, is part of an eight prime value family.
My solution was written in Java; extensive thoughts and notes here: https://charlesreid1.com:3000/cs/euler/src/master/scratch/Round2_050-070/051
Note that the wording of this problem is a bit tricky...
Project Eulerproject euler notes
Round 1: Problems 1-20
Round 2: Problems 50-70
Round 3: Problems 100-110
Round 4: Problems 500-510
Round 5: Problems 150-160
Round 6: Problems 250-260
Round 7: Problems 170-180