Originally Posted by Happy5214 No luck: Code: \$ ./srsieve2 -i b2_n.abcd -o b2_n.abcd -R "658687*2^n-1" srsieve2 v1.5.1, a program to find factors of k*b^n+c numbers for fixed b and variable k and n 2018 terms for sequence 658687*2^n-1 have been removed Must use generic sieving logic because there is more than one sequence Sieving with generic logic for p >= 982453051 Fatal Error: Expected 62636 terms when building sequences, but counted only 60618 Input file attached (with .txt extension added).