MathDB
2022-digit interesting numbers of Puerto Rico TST 2022.2.1

Source:

March 23, 2024
number theory

Problem Statement

Let's call a natural number interesting if any of its two digits consecutive forms a number that is a multiple of 1919 or 2121. For example, The number 76387638 is interesting, because 7676 is a multiple of 1919, 6363 is multiple of 2121, and 3838 is a multiple of 1919. How many interesting numbers of 20222022 digits exist?
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