Jump to Content

Repeatedly Appending Any Digit to Generate Composite Numbers

John Grantham
Witold Jarnicki
Jon Rickert
Stan Wagon
The American Mathematical Monthly (2012) (to appear)

Abstract

We investigate the problem of nding integers k such that ap- pending any number of copies of the base-ten digit d to k yields a composite number. In particular, we prove that there exist in nitely many integers co- prime to all digits such that repeatedly appending any digit yields a composite number.