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<p>Here,  is the <a href="page.php?w=big_O_notation">big {{mvar</a>.</p>

<p>More precise estimates of  are now known. For example, in 2002, <a href="page.php?w=Kevin_Ford_%28mathematician%29">Kevin Ford</a> proved that</p>

<p>Mossinghoff and <a href="page.php?w=Timothy_Trudgian">Trudgian</a> proved an explicit upper bound for the difference between  and :</p>

<p>For values of  that are not unreasonably large,  is greater than . However,  is known to change sign infinitely many times. For a discussion of this, see <a href="page.php?w=Skewes%27_number">Skewes' number</a>.</p><p>
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