Friday, February 6

(101*10^120072-87)/7 is prime

A good part of my dabbling in recreational arithmetic is searching for large primes. My previous best was 2*(10^39960+10^63+10^36+10^12)+2223 which has 39961 digits and dates to October 2011. Today I bettered that with (101*10^120072-87)/7 which is made up of 120074 digits — large enough to be on page three of Henri & Renaud Lifchitz's top probable prime records. The find arises out of an observation I made for A254005.