Erdos conjectured that there are \( \gg_\epsilon x^{1-\epsilon}\) carmichael numbers up to \( x\), whereas Shanks, based on calculations, was skeptical as to whether one might even find an \( x\) up to which there are \( x^{1/2}\) Carmichael numbers. In this article we show that they were both correct, in that by understanding the structure of Carmichael numbers one sees why there will only be a lot of Carmichael numbers for very large \( x\).
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