Invitation: celebrating 50 years of OEIS, 250000 sequences, and Sloane's 75th, there will be a conference at DIMACS, Rutgers, Oct 9-10 2014.

A085107

Starting with n-1 go on adding the numbers less than n and coprime to it in descending order until one gets a prime. a(n) = this prime, or 0 if no such number exists.