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Sum of digits of a square number.

Discussion in 'Mathematics' started by Math Tise, Oct 8, 2018.

  1. Math Tise

    Math Tise Guest

    A positive integer n is said to be good if there exists a perfect square whose sum of digits in base 10 is equal to n. For instance, 13 is good because (7^2)=49 and 4+9=13. How many good numbers are among 1, 2, 3, …, 2007?

    I have started to make a list of all square numbers and adding their digits in an excel file. ... Until now, I have got good numbers as 1, 4, 7, 9, 10, 13, 16, 19. But, this method takes very long. ... Is there a shorter and smarter way to solve this problem.

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