MathDB
digits

Source:

March 5, 2005
AMCAIMEUSA(J)MOUSAMOmodular arithmeticLaTeXbinomial coefficients

Problem Statement

Prove that for all a{0,1,2,,9}a\in\{0,1,2,\ldots,9\} the following sum is divisible by 10: Sa=a2005+1a2005+2a2005++9a2005. S_a = \overline{a}^{2005} + \overline{1a}^{2005} + \overline{2a}^{2005} + \cdots + \overline{9a}^{2005}.