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digit ''5'' in the result of sum 1 + 10 + 19 + 28 + 37 +...+ 10^{2013}

Source: Dutch NMO 2013 p5

September 6, 2019
Sumnumber theoryDigit

Problem Statement

The number SS is the result of the following sum: 1+10+19+28+37+...+1020131 + 10 + 19 + 28 + 37 +...+ 10^{2013} If one writes down the number SS, how often does the digit `55' occur in the result?
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