Repeatedly Appending Any Digit to Generate Composite Numbers
The American Mathematical Monthly(2012) (to appear)
John Grantham, Witold Jarnicki, Jon Rickert, Stan Wagon
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 innitely many integers co- prime to all digits such that
repeatedly appending any digit yields a composite number.