MathDB
Problems
Contests
Undergraduate contests
Putnam
1989 Putnam
A1
10101...101
10101...101
Source: Putnam
November 11, 2007
Putnam
algebra
difference of squares
special factorizations
college contests
Problem Statement
How many base ten integers of the form 1010101...101 are prime?
Back to Problems
View on AoPS