# Are you lucky enough to find these lucky numbers?

Discrete Mathematics Level 4

A natural number $$a$$ is called a lucky number if the sum of its digits is 7. Arrange all lucky numbers in an ascending order, and we get a sequence $$a_1 , a_2 , a_3 , \ldots$$. If $$a_n = 2005$$, compute $$a_{5n}$$.

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