A number n is groovy iff the sum of the digits of n(2n+1) is 2018. Do such numbers exist and, if so, what are they?
closed as off-topic by GNUSupporter 8964民主女神 地下教會, YiFan, Jyrki Lahtonen, José Carlos Santos, A. Pongrácz Feb 15 at 9:51
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