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IMC 2007 — Keystage 3 (IWYMIC) — individual Question 12

xIMC · IMC 2007 — Keystage 3 (IWYMIC) — individual

Question 12

A positive integer $n$ is good if some perfect square has decimal digit sum $n$. For example, thirteen is good because $7^2=49$ and $4+9=13$. How many good numbers are among $1,\ldots,2007$?